Question

I am currently taking a practice test. The question is to find the x and y intercepts of the graph y=3x^2+6x-9. They say that the answer is x=-3 or x=2 and y=(0,-9). I get that x=1 or x=-3 and y=-9. What did i do wrong?

Answer 1

y-intercept when x=0
y=-9
(0,9)

Answer 2

Right.

Answer 3

x-intercept when y=0
x=-3,1
(-3,0) and (1,0)

Answer 4

You are given \(f(x)=3x^2+6x-9\). To find the \(x\)-intercepts, you have to set \(3x^2+6x-9=0\implies3(x-1)(x+3)=0\implies x=1\text{ and }x=-3\). To find the \(y\)-intercept, you evaluate the function at \(0\): \(f(0)=-9\).

Answer 5

Thank You. I thought that I was going crazy... Thank you!