SOLUTION: 3. The graph of y=x^2+2x-8 intersects the x-axis at (1) 2 and -4 (2) -2 and 4 (3) -2 and -4 (4) 2 and 4 Please show steps.

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: 3. The graph of y=x^2+2x-8 intersects the x-axis at (1) 2 and -4 (2) -2 and 4 (3) -2 and -4 (4) 2 and 4 Please show steps.      Log On


   

Question 227187: 3. The graph of y=x^2+2x-8 intersects the x-axis at
(1) 2 and -4
(2) -2 and 4
(3) -2 and -4
(4) 2 and 4
Please show steps.
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
set x^2 + 2x - 8 = 0

this would be the point at which the equations crosses the x-axis.

factor x^2 + 2x - 8 to get
(x+4) * (x-2) = 0

solving this equation will make both of these terms equal to 0.

example:

divide both sides of the equation by (x-2) and you get (x+4) = 0
divide both sides of the equation by (x+4) and you get (x-2) = 0

x+4 = 0 results in x = -4
x-2 = 0 results in x = 2

that would be selection (1)

a graph of the equation is shown below.

graph+%28300%2C300%2C-10%2C10%2C-10%2C10%2Cx%5E2+%2B+2x+-+8%29

as can be seen, the graph of the equation x^2 + 2x - 8 crosses the x-axis at x = 2 and x = -4