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12 votes
12 votes
For for each quadratic function below use method of completing the Square or averaging the x-intercept to write the equation in the Graphing form. then, State Line of symmetry and give the vertex of each parabola. try to use the method at least one.
a.f(x) = {x}^(2) + 6 x + 15
b.y = {x}^(2) - 4x +9
c.f(x) = {x}^(2) - 8x
d.y = {x}^(2) + 7x - 2

User GreenFox
by
3.3k points

1 Answer

30 votes
30 votes

We have the expressions:


f(x)=x^2+6x+15
y=x^2-4x+9
f(x)=x^2-8x
y=x^2+7x-2

Now, with this we operate as follows:

a)


f(x)=x^2+6x+15=x^2+6x+9+15-9
\Rightarrow(x+3)^2+6

Then, the axis is x = -3 and the vertex (-3, 6)

b)


y=x^2-4x+9=x^2-4x+4+9-4
\Rightarrow(x-2)^2+5

Then, the vertex is (2, 5) and the axis is x = 2.

c)


f(x)=x^2-8x+4-4\Rightarrow(x-2)^2-4

Then, the vertex is (2, -4) andd the axis is x = 2.

d)


y=x^2+7x-2=x^2+7x+(49)/(4)-2-(49)/(4)
\Rightarrow(x+(7)/(2))^2-(57)/(4)

Then, the vertex is (-7/2, -57/4) and the axis is -7/2.

User Abimbola
by
2.9k points
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