SOLUTION: Write the equation in standard form y = ax^2 + bx + c if the roots are -4 and -2 and it passes through (-1, 3) A. y = x^2 - 6x + 8 B. y = x^2 + 6x - 8 C. y = x^2 + 6x + 8

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Write the equation in standard form y = ax^2 + bx + c if the roots are -4 and -2 and it passes through (-1, 3) A. y = x^2 - 6x + 8 B. y = x^2 + 6x - 8 C. y = x^2 + 6x + 8       Log On


   

Question 1206376: Write the equation in standard form y = ax^2 + bx + c if the roots are -4 and -2 and it passes through (-1, 3)
A. y = x^2 - 6x + 8
B. y = x^2 + 6x - 8
C. y = x^2 + 6x + 8
D. y = x^2 - 6x - 8
Found 2 solutions by josgarithmetic, MathLover1:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
You can start with an expression a%28x%2B4%29%28x%2B2%29=y, and find "a" value using the "passes through" given point.

a%28-1%2B4%29%28-1%2B2%29=3
a%283%29%281%29=3
a=1

With that you have y=%28x%2B4%29%28x%2B2%29;
doing the multiplication,
x%5E2%2B4x%2B2x%2B8
x%5E2%2B6x%2B8-----------------choice C.

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

given:
x%5B1%5D=-4 and x%5B2%5D=-2
point (-1, 3)
using root product equation we have
y=a%28x-x%5B1%5D%29%28x-x%5B1%5D%29+...plug in given roots and coordinates of given point to calculate a
3=a%28-1-%28-4%29%29%28-1-%28-2%29%29+
3=a%28-1%2B4%29%28-1%2B2%29+
3=a%283%29%281%29+
3=3a
a=1
go to
y=a%28x-x%5B1%5D%29%28x-x%5B1%5D%29+...substitue a and roots
y=1%28x-%28-4%29%29%28x-%28-2%29%29
y=%28x%2B4%29%28x%2B2%29
y=x%5E2+%2B+6x+%2B+8
=> answer is C.