Pearson Algebra 1 Common Core, 2011
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Pearson Algebra 1 Common Core, 2011 View details
3. Solving Quadratic Equations
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Exercise 56 Page 566

Practice makes perfect
a We start to solve the quadratic equation (x-7)^2=0 by finding the square roots of each side.
(x-7)^2=0 ⇔ x-7=0 We have found the equivalent equation x-7=0. We can solve it with one step. x-7=0 ⇔ x=7 Since the equation x-7=0 holds true for x=7, this is the solution for the original quadratic equation as well.
b To find the location of the vertex of the related quadratic function y =(x-7)^2, we first need to write the quadratic function in standard form. To do this we can use the rule for the square of a binomial.

y =(x-7)^2
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Rewrite
y =x^2-2* x *7 +7^2
y =x^2-2* x *7 +49
y =x^2-14x+49

Now that we have our function in standard form, we can compare it to the general form to identify the parameters a and b. This will let us find the vertex by using the formula for the x-coordinate of the vertex. Let's identify the parameters needed.

ax^2+ bx+c 1x^2+( - 14)x+49 As we can see, a= 1 and b= -14. Now, we are ready to use the formula for the x-coordinate of the vertex. V_x = - b/2a Let's give it a try.

V_x = - b/2a
V_x = -( -14)/2( 1)
V_x = 14/2
V_x = 7

Finally, we can use this x-value to find the y-coordinate by evaluating the function.

y = (x-7)^2
y = ( 7-7)^2
y = (0)^2
y = 0

Therefore, the vertex is located at (0,7).

c Let's try using h=-3. We can start by finding the corresponding equation.

(x-h)^2 ⇓ (x-(-3))^2 ⇕ (x+3)^2 = 0 Now, we can solve for x, in the same way we did in Part A.

(x+3)^2 = 0
x+3 = 0
x= - 3
Hence, the solution for the quadratic equation (x+3)^2=0 is x= - 3. Furthermore, since the related function is y=(x+3)^2, we can rewrite it in standard by expanding the square binomial, just as we did in Part B. The result is shown below. y=(x+3)^2 ⇔ y=x^2+6x+9 Now, comparing the function to the standard form we can identify the parameters a and b. y = ax^2+ bx+c y= 1x^2+ 6x+9 As we can see, a = 1 and b= 6. With this we are ready to find the x-coordinate of the vertex.

V_x = - b/2a
V_x = - ( 6)/2( 1)
V_x = 6/2
V_x = 3

Finally, we can find the corresponding y-coordinate of the vertex by evaluating the function.

y = (x+3)^2
y = (-3+3)^2
y = 0^2
y = 0

Therefore, the vertex is located at (- 3,0).

d Let's take a look at the results from Parts B and C.
Quadratic Function Vertex
y = (x-7)^2 (7,0)
y = x+3 ⇕ y = x-(- 3) (- 3,0)
The results suggest that a quadratic function of the form y=(x-h)^2 has its vertex located at the point (h,0). Let's have a look at the function given. y = (x +4)^2 ⇔ y = (x - (-4))^2 Notice that it is of the form y=(x-h)^2 as well. y=(x- h)^2 y=(x-( -4))^2 Therefore, we can expect it to have its vertex at ( -4,0).