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| | 9 Theory slides |
| | 9 Exercises - Grade E - A |
| | Each lesson is meant to take 1-2 classroom sessions |
Consider two different polynomials P(x) and Q(x). P(x) &= 5x^3-2x+7 [0.1cm] Q(x) &= 3(x-1)(x+4) Is it possible to calculate the sum and the difference of P(x) and Q(x)? Are the obtained results also polynomials? If yes, what is the degree, the leading coefficient, and the constant term of P(x)+Q(x)?
Given two polynomials, their sum or difference can be calculated. Consider the following pair of polynomials. - 2x^2 + x + 3 and 2x^2 + 4x - 10 In order to add these polynomials, there are three steps to follow. Note that subtraction of the polynomials can be performed by applying the same three steps, only instead of adding the like terms, they will be subtracted.
Remove parentheses
Commutative Property of Addition
When subtracting polynomials, remember to distribute - 1 to the terms of the second polynomial before rearranging the terms.
Remove parentheses
Distribute - 1
Commutative Property of Addition
Therefore, the sum is 5x-7. Note that the given polynomials are of degree 2. However, the new polynomial is of degree 1 because the x^2-terms canceled each other out. If they had not canceled each other out, the new polynomial would have also been of degree 2.
Is the result of addition or subtraction of polynomials always another polynomial? This can be verified by analyzing the sum of two arbitrary polynomials. 3x^3+5x^2-x+7 and 12x^2+6x-3 To add these polynomials, their like terms will be rearranged to be next to each other and then added.
Remove parentheses
Commutative Property of Addition
Add and subtract terms
Dylan's family is moving into an apartment. He is curious about how many people live in apartements as opposed to houses. He finds a study that states that during a 6-year period, the amounts of money in millions of dollars spent on buying houses B and renting houses R by United States residents are modeled by the following two polynomials.
B&=- 0.023n^3+0.08n^2+0.1n+15 R&=- 0.41n^2+1.3n+36 Here, n=1 represents the first year in the 6-year period.
Remove parentheses
Commutative Property of Addition
Add and subtract terms
a+(- b)=a-b
Note that the polynomial is written in standard form as the degrees of its monomials decrease moving from left to right.
- &0.41n^2+1.3n+36 + (- 0.023n^3+&0.08n^2+0.1n+15) - 0.023n^3-&0.33n^2+1.4n+51
B + R = - 0.023n^3 - 0.33n^2 + 1.4n + 51 R + B = - 0.023n^3 - 0.33n^2 + 1.4n + 51 As can be seen, these sums are the same polynomial. Recall that addition of real numbers is commutative. Since adding polynomials comes down to adding the coefficients of like terms, which are real numbers, it can be concluded that the addition of polynomials is also commutative.
- 0.023n^3-0.33n^2+1.4n+51 Therefore, the degree of this polynomial is 3. The leading coefficient of a polynomial is the coefficient of the term with the highest degree. Since the first term has the highest degree, the leading coefficient is - 0.023. - 0.023n^3-0.33n^2+1.4n+51
Dylan is delighted to find out that one of his classmates lives in his apartment building, although they live on different floors. They decided to run a little experiment for their science class. Both of them would drop an object from their window at the same time and would see whose object reached the ground first.
Substitute expressions
Remove parentheses
Distribute - 1
Commutative Property of Addition
Add and subtract terms
- 16x^2+ 0x&+100 - - 16x^2-45x &+180 45x &- 80
T(x)-P(x)&=- 45x+80 P(x)-T(x)&=45x-80 The polynomials are different. This suggests that when subtracting polynomials, their order does matter. In other words, the subtraction of polynomials is not commutative.
T(x)-P(x)&=- 45x^1+80 P(x)-T(x)&=45x^1-80 The degree of each polynomial is 1. Next, recall that the leading coefficient of a polynomial is the coefficient of the term with the highest degree. T(x)-P(x)&= - 45x+80 P(x)-T(x)&= 45x-80 In the first polynomial, the leading coefficient is - 45, while it is 45 in the second polynomial.
Consider the sum or difference of the given polynomials. Identify their degree or leading coefficient.
In the evening, Dylan is reading his apartment complex's newsletter on his tablet and finds a small mathematical riddle. Readers who solve it correctly can get a 50 % discount for a highly innovative online course called Smart Applications of Math.
The polynomial corresponding to P-Q-R can be calculated in a similar manner, this time subtracting the terms. Consider how the sign of each term might be affected by the subtraction sign — remember, subtracting a negative number is the same as adding the terms. There are three rows of polynomials, but the subtraction will be done by considering only two terms at a time.
Next, the polynomial Q will be added to P and then R will be subtracted. Remember to carefully consider the signs of the terms when subtracting R.
Finally, the polynomial P-Q+R will be calculated.
With the information presented in the lesson, the challenge given in the beginning can finally be solved. The challenge was to calculate the sum and the difference of the two given polynomials P(x) and Q(x). P(x) &= 5x^3-2x+7 [0.1cm] Q(x) &= 3(x-1)(x+4) Furthermore, if P(x)+Q(x) is also a polynomial, what are its degree, leading coefficient, and constant term?
Substitute expressions
Commutative Property of Addition
Add and subtract terms
By the Closure Property of Polynomial Addition, the obtained result is also a polynomial. The highest degree of its monomials is 3, so 3 is the degree of P(x)+Q(x). The coefficient of the monomial with the highest degree is 5, so the leading coefficient is 5. Moreover, the constant term is - 5.
Now, the difference of P(x) and Q(x) can be found following a similar procedure. For simplicity, the previously found standard form of Q(x) will be used.
Substitute expressions
Remove parentheses
Distribute - 1
Commutative Property of Addition
Add and subtract terms
The obtained expression consists of monomials, so it is also a polynomial. P(x) + Q(x)& = 5x^3 + 3x^2 + 7x - 5 P(x) - Q(x)& = 5x^3 - 3x^2 - 11 x+ 19
We want to find the leading coefficient of the sum of P(x)+Q(x). Let's start by calculating the sum of the polynomials.
We found an expression for the sum P(x)+Q(x). The leading coefficient is the number that multiplies the power with the greatest exponent. P(x)+Q(x)= 4x+2 The leading coefficient of the sum is 4.
In Part A we calculated the sum of the polynomials. Now we want to find the degree of the expression. Recall that the degree of a polynomial is the exponent of the greatest power of the variable, which in this case is x. When a variable has no exponent, it means that the exponent is 1.
P(x)+Q(x)=4x+2 ⇕ P(x)+Q(x)=4x^1+2
The degree of the expression that represents the sum is 1.
We want to find the leading coefficient of the difference of P(x)-Q(x). We will start by calculating the difference of the polynomials. Remember to write both polynomials in parentheses. Then we can distribute - 1 and simplify the expression.
We found an expression for the difference P(x)-Q(x). The leading coefficient is the number that multiplies the power with the greatest exponent. P(x)-Q(x)= - 6x^2-4 The leading coefficient of the difference is - 6.
In Part A we calculated the difference of the polynomials. Now we want to find the degree of the expression. Recall that the degree of a polynomial is the exponent of the greatest power of the variable, which in this case is x.
P(x)-Q(x)=- 6x^2-4
The degree of the difference is 2.
To add the given polynomials, we will start by writing both of them in parentheses. Then we will remove the parentheses and rearrange the terms by using the Commutative Property of Addition. Finally, we will add and subtract like terms. Let's do it!
The sum of the polynomials is -2x+7.
As in Part A, we will start by writing both polynomials in parentheses. Then we will remove the parentheses and rearrange the terms by using the Commutative Property of Addition. Finally, we will add and subtract like terms.
The sum of the polynomials is 3x^3-x^2+3x-9.
To subtract the given polynomials, we will start by writing both of them in parentheses. Then we will distribute - 1 to Q(x), remove the parentheses, and rearrange the terms by using the Commutative Property of Addition. Finally, we will add and subtract like terms. Let's do it!
The difference of the polynomials is 10x+3.
As in Part A, we will write both polynomials in parentheses. Then we will distribute - 1 to Q(x), remove the parentheses, and rearrange the terms by using the Commutative Property of Addition. Finally, we will add and subtract like terms.
The difference of the polynomials is 3x^3-7x^2-x+9.
The cost in dollars of making x shirts is represented by 5+4x. The cost in dollars of making x sweaters is represented by 6x+8. Write a polynomial that represents how much more it costs to make x sweaters than x shirts.
We want to write a polynomial that represents how much more it costs to make x sweaters than x shirts. To do so, we will subtract the cost to make x shirts from the cost to make x sweaters. Let's write an expression to illustrate this situation. We will start by isolating each expression in parentheses first. x sweaters -& xshirts [0.5em] (6x+8) -& (5+4x) We can simplify this expression by distributing - 1 to the expression representing the cost to make the shirts in order to remove the parentheses, then using the Commutative Property of Addition to rearrange the terms. Finally, we will add and subtract like terms to simplify the resulting polynomial. Let's do it!
We can conclude that the difference between the cost of making x sweaters and the cost of making x shirts is 2x+3 dollars.
Complete the statement with never, sometimes, or always.
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Every term of a polynomial is a monomial. |
Let's start by recalling the definitions of a monomial and a polynomial.
| Monomial | Polynomial | |
|---|---|---|
| Definition | A monomial is a number, a variable, or the product of a number and one or more variables with whole number exponents. | A polynomial is a monomial or a sum of monomials. Each monomial is called a term of the polynomial. |
| Degree | The degree of a monomial is the sum of the exponents of the variables in the monomial. The degree of a non-zero constant term is 0. The constant 0 does not have a degree. | The degree of a polynomial is the greatest degree of its terms. |
| Standard Form | - | A polynomial in one variable is in standard form when the exponents of the terms decrease from left to right. |
| Leading Coefficient | The coefficient of the monomial. | When a polynomial is written in standard form, the coefficient of the first terms is the leading coefficient. |
Since a polynomial is a monomial or a sum of monomials, we can conclude that every term of a polynomial is always a monomial.
Every term of a polynomial is always a monomial.