Core Connections Algebra 1, 2013
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Core Connections Algebra 1, 2013 View details
2. Section 8.2
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Exercise 85 Page 397

Practice makes perfect
a We want to solve the given equation for x. Since the equation is already written in factored form, we will use the Zero Product Property.

(6x-18)(3x+2)=0
lc6x-18=0 & (I) 3x+2=0 & (II)
â–¼
(I): Solve for x
l6x=18 3x+2=0
lx=3 3x+2=0
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(II): Solve for x
lx=3 3x=- 2
lx=3 x= - 23
lx_1=3 x_2=- 23
We found that x=3 or x=- 23. We can substitute our solutions back into the given equation and simplify to check if our answers are correct. We will start with x=3.

(6x-18)(3x+2)=0
(6( 3)-18)(3( 3)+2)? =0
â–¼
Simplify
(18-18)(9+2)? =0
(0)(11)? =0
0=0 ✓

Substituting and simplifying created a true statement, so we know that x=3 is a solution of the equation. Let's move on to x=- 23.

(6x-18)(3x+2)=0
(6( - 2/3)-18)(3( - 2/3)+2)? = 0
â–¼
Simplify
(6(- 2/3)-18)(3( - 2/3)+2)? = 0
(2 * 3(- 2/3)-18)(3( - 2/3)+2)? = 0
(2 * (- 2)-18)(- 2+2)? = 0
(- 4-18)(- 2+2)? = 0
(- 22)(0)? = 0
0=0 ✓

Again, we created a true statement. x=- 23 is indeed a solution of the equation.

b We want to solve the given equation for x. To do this, we can start by using factoring. Then, we will use the Zero Product Property.

Factoring

To factor a trinomial with a leading coefficient of 1, think of the process as multiplying two binomials in reverse. Let's start by taking a look at the constant term. x^2-7x+10=0 In this case, we have 10. This is a positive number, so for the product of the constant terms in the factors to be positive, these constants must have the same sign (both positive or both negative.)

Factor Constants Product of Constants
1 and 10 10
-1 and -10 10
2 and 5 10
-2 and -5 10

Next, let's consider the coefficient of the linear term. x^2-7x+10=0 For this term, we need the sum of the factors that produced the constant term to equal the coefficient of the linear term, - 7.

Factors Sum of Factors
1 and 10 11
-1 and -10 -11
2 and 5 7
- 2 and - 5 - 7

We found the factors whose product is 10 and whose sum is - 7. x^2-7x+10=0 ⇕ (x-2)(x-5)=0

Zero Product Property

Since the equation is already written in factored form, we can now use the Zero Product Property.

(x-2)(x-5)=0
lcx-2=0 & (I) x-5=0 & (II)
lx=2 x-5=0
lx_1=2 x_2=5

We found that x=2 or x=5.

Checking Our Answer

We can substitute our solutions back into the given equation and simplify to check if our answers are correct. We will start with x=2.

x^2-7x+10=0
2^2-7( 2)+10? =0
â–¼
Simplify
4-7(2)+10? = 0
4-14+10? = 0
0=0 ✓

Substituting and simplifying created a true statement, so we know that x=2 is a solution of the equation. Let's move on to x=5.

x^2-7x+10=0
5^2-7( 5)+10? = 0
â–¼
Simplify
25-7(5)+10? = 0
25-35+10? = 0
0=0 ✓

Again, we created a true statement. x=5 is indeed a solution of the equation.

c We want to solve the given equation for x. To do this, we can start by using factoring. Then, we will use the Zero Product Property. Let's start factoring by identifying the greatest common factor (GCF).

Factor Out The GCF

The GCF of an expression is a common factor of the terms in the expression. It is the common factor with the greatest coefficient and the greatest exponent. In this case, the GCF is 2.

2x^2+2x-12=0
2* x^2+ 2* x- 2* 6=0
2(x^2+x-6)=0

The result of factoring out a GCF from the given expression is a trinomial with a leading coefficient of 1. 2( x^2+x-6)=0

Let's temporarily only focus on this trinomial, and we will bring back the GCF after factoring.

Factor The Expression

To factor a trinomial with a leading coefficient of 1, think of the process as multiplying two binomials in reverse. Let's start by taking a look at the constant term. x^2+x- 6=0 In this case, we have -6. This is a negative number, so for the product of the constant terms in the factors to be negative, these constants must have the opposite sign (one positive and one negative.)

Factor Constants Product of Constants
- 1 and 6 - 6
1 and -6 - 6
- 2 and 3 - 6
2 and -3 - 6

Next, let's consider the coefficient of the linear term. x^2+1x- 6=0 For this term, we need the sum of the factors that produced the constant term to equal the coefficient of the linear term, 1.

Factors Sum of Factors
- 1 and 6 5
1 and -6 -5
- 2 and 3 1
2 and -3 - 1

We found the factors whose product is - 6 and whose sum is 1. x^2+1x- 6=0 ⇕ (x-2)(x+3)=0 Wait! Before we finish, remember that we factored out a GCF from the original equation. To fully complete the factored equation, let's reintroduce that GCF now. 2(x-2)(x+3)=0

Zero Product Property

Since the equation is already written in factored form, we can now use the Zero Product Property.

2(x-2)(x+3)=0
(x-2)(x+3)=0
lcx-2=0 & (I) x+3=0 & (II)
lx=2 x+3=0
lx_1=2 x_2=- 3

We found that x=2 or x=- 3.

Checking Our Answer

We can substitute our solutions back into the given equation and simplify to check if our answers are correct. We will start with x=2.

2x^2+2x-12=0
2( 2)^2+2( 2)-12? =0
â–¼
Simplify
2(4)+2(2)-12? = 0
8+4-12? = 0
0=0 ✓

Substituting and simplifying created a true statement, so we know that x=2 is a solution of the equation. Let's move on to x=- 3.

2x^2+2x-12=0
2( - 3)^2+2( - 3)-12? =0
â–¼
Simplify
2(9)+2(- 3)-12? = 0
2(9)-6-12? = 0
18-6-12? = 0
0=0 ✓

Again, we created a true statement. x=- 3 is indeed a solution of the equation.

d We want to solve the given equation by factoring.

Applying the Difference of Two Squares

Do you notice that the expression on the left-hand side of the equation is a difference of two perfect squares? This can be factored using the difference of squares method. a^2 - b^2 ⇔ (a+b)(a-b)To do so, we first need to express each term as a perfect square.

Expression 4x^2-1
Rewrite as Perfect Squares (2x)^2 - 1^2
Apply the Formula (2x+1)(2x-1)

Solving the Equation

Finally, to solve the equation, we will use the Zero Product Property.

4x^2-1=0
â–¼
a^2-b^2=(a+b)(a-b)
2^2x^2-1^2=0
(2x)^2-1^2=0
(2x+1)(2x-1)=0
lc2x+1=0 & (I) 2x-1=0 & (II)
l2x=- 1 2x-1=0
l2x=- 1 2x=1

(I), (II): .LHS /2.=.RHS /2.

lx_1=- 12 x_2= 12

Checking Our Answer

We can substitute our solutions back into the given equation and simplify to check if our answers are correct. We will start with x=- 12.

4x^2-1=0
4( -1/2)^2-1? =0
â–¼
Simplify
4 ( 1/4 )-1? = 0
1-1? = 0
0=0 ✓

Substituting and simplifying created a true statement, so we know that x=- 12 is a solution of the equation. Let's move on to x= 12.

4x^2-1=0
4( 1/2)^2-1? =0
â–¼
Simplify
4 ( 1/4 )-1? = 0
1-1? = 0
0=0 ✓

Again, we created a true statement. x= 12 is indeed a solution of the equation.