SOLUTION: Find the x intercepts f(x)=2x^2 +8x-42 (2x+6)(x-7) x+3 X-7 intercepts are - 3 and 7 is this correct?????

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Find the x intercepts f(x)=2x^2 +8x-42 (2x+6)(x-7) x+3 X-7 intercepts are - 3 and 7 is this correct?????      Log On


   

Question 194574: Find the x intercepts
f(x)=2x^2 +8x-42
(2x+6)(x-7)
x+3 X-7
intercepts are - 3 and 7 is this correct?????
Found 2 solutions by stanbon, jojo14344:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Find the x intercepts
f(x)=2x^2 +8x-42
---
Let y = 0
2x^2 + 8x - 42 = 0
2(x^2 + 4x - 21) = 0
Factor:
2(x+7)(x-3) = 0
x = -7 or x = 3
========================
Cheers,
Stan H.

Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!


Given: f(x)=2x^2 +8x-42
Simplified by dividing the whole eqn by 2:

x%5E2%2B4x-21=0, perfect square
So, %28x%2B7%29%28x-3%29=0
Then, red%28x=-7%29; red%28x=3%29, X-Intercepts.

To follow up on this, let us find the vertex: a%28x-h%29%5E2%2Bk

Complete the square:
%28x%5E2%2B4x%2Bhighlight%284%29%29-21-highlight%284%29
%28x%2B2%29%5E2-25

Vertex: (-2,-25)

Since a>0, (a=1), the parabola opens upwards.


Thank you,
Jojo