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| 11 Theory slides |
| 10 Exercises - Grade E - A |
| Each lesson is meant to take 1-2 classroom sessions |
Here are a few recommended readings before getting started with this lesson.
One afternoon, Jordan was playing soccer in front of her building with some friends. She wanted to invite her neighbor Mark over to play. To do so, she kicked the ball upward as hard as she could, trying to get Mark to see it outside his window. That kick followed the path of the quadratic equation h=6t−t2.
Here, h is the height in meters of the ball above the ground and t is the time in seconds after the kick. If Mark's bedroom window is 10 meters above the ground, could Mark see the ball? If so, find the value of t for the amount of time it takes for the ball to reach Mark's bedroom window. If not, select No real roots.
Substitute values
Calculate power and product
-(-a)=a
Subtract term
Later that evening, she was still in awe at the Quadratic Formula and wrote it on a chalkboard in her room. She then began to think about the cases in which the discriminant is negative. After analyzing the fact that there are two signs in front of the radical term, she came to another brilliant conclusion.
Substitute values
Calculate power and product
Subtract term
-a=a⋅i
Split into factors
a⋅b=a⋅b
Calculate root
Factor out 2
Simplify quotient
a2+b2=(a+bi)(a−bi)
Maya is reviewing the responses to the last two-question quiz on solving quadratic equations that her math students took through the school's online platform.
Perfect Square Trinomial a2±2ab+b2=(a±b)2 | ||
---|---|---|
Equation | Factorization | Solutions |
x2+6x+9=0 | (x+3)2=0 | x1=x2=-3 |
x2−8x+16=0 | (x−4)2=0 | x1=x2=4 |
x2±2bix−b2=(x±bi)2
Seeing Jordan's enthusiasm for solving quadratic equations, her older sister Dominika wanted to set her an interesting challenge.
Feeling confident, Jordan accepted the challenge.
LHS−4=RHS−4
Split into factors
Rewrite 36 as 62
LHS+25=RHS+25
Rewrite 4 as 22
x2+2bix−b2=(x+bi)2
LHS=RHS
LHS−2i=RHS−2i
Factor each quadratic equation.
In the challenge presented, it was said that Jordan kicked the ball up as hard as she could, trying to make it visible from Mark's bedroom window. Mark's window is 10 meters above the ground. Additionally, it is known that the ball followed the path of the quadratic equation h=6t−t2.
Substitute values
Calculate power and product
Subtract term
It can also be determined graphically if the equation 10=6t−t2 has real solutions. To do so, graph y=10 and y=6t−t2 on the same coordinate plane.
LHS+t2−6t=RHS+t2−6t
Use the Quadratic Formula: a=1,b=-6,c=10
Calculate power and product
Subtract term
-(-a)=a
-a=a⋅i
Calculate root
Factor out 2
ba=b/2a/2
Determine the values of m for the following cases.
We can tell the number of real solutions a quadratic equation has by calculating its discriminant. For a quadratic equation of the form a^2+bx+c=0, the discriminant is given by the following expression. b^2-4ac We can find the different scenarios regarding the number and type of solutions to a quadratic equation depending on the discriminant value.
Discriminant | Number of Real Solutions |
---|---|
b^2-4ac >0 | There are two real solutions. |
b^2-4ac = 0 | There is one real solution. |
b^2-4ac < 0 | There are no real solutions. |
Comparing the expression 7x^2+ mx+ 9 with ax^2+ bx+ c, we can see that a= 7, b= m, and c= 9. For the equation to have no real solutions, the discriminant must be less than zero. This meets the condition b^2-4ac < 0. Let's see the what this means for the possible values of m.
Since squaring a number always gives a positive result, we can conclude that the absolute value of m is less than 6sqrt(7) for the equation to have no real solutions. In other words, m must be less than 6sqrt(7) and greater than -6sqrt(7). This can also be written in as an interval.
- 6sqrt(7)
As we discussed in Part A, we have the discriminant of the equation b^2-4ac must equal zero for the quadratic equation to have exactly one real solution. Let's find the possible values of m that make the discriminant equal 0.
We have concluded that the absolute value of m is equal to 6sqrt(7) in order for the equation to satisfy the given condition. Therefore, if m=6sqrt(7) or m=-6sqrt(7) the equation will have just one solution.
As we discussed in Part A, the discriminant of the equation b^2-4ac must be greater than zero in order for the quadratic equation to have two real solutions. Let's find the possible values of m that match this condition.
Since squaring a number always gives a positive result, we need the absolute value of m to be greater than 6sqrt(7) for the equation to satisfy the given condition. This means that the values for m that satisfy the equation are m<- 6sqrt(7) or m>6sqrt(7).