Finding x & y intercepts (found the y-intercept)

**lilrhino** · June 21st 2007, 01:31 PM

I need help please with finding the x-intercept for the following:

$y = -2x^2 +4$

I got the y-intercept (0,4) by setting x = 0

However, when I set y = 0 and attempt to solve I get stuck

$0 = -2x^2 + 4$

What are the next steps for finding the x-intercept? Thanks in advance!

**Plato** · June 21st 2007, 02:52 PM

$x= \pm \sqrt 2$ ?

**Jhevon** · June 21st 2007, 07:36 PM

Originally Posted by lilrhino

I need help please with finding the x-intercept for the following:

$y = -2x^2 +4$

I got the y-intercept (0,4) by setting x = 0

However, when I set y = 0 and attempt to solve I get stuck

$0 = -2x^2 + 4$

What are the next steps for finding the x-intercept? Thanks in advance!

$0 = -2x^2 + 4$ .........subtract 4 from both sides

$\Rightarrow -4 = -2x^2$ .........Now divide through by -2

$\Rightarrow 2 = x^2$ .............Now take the squareroot of both sides

$\Rightarrow \pm \sqrt {2} = x$

So our x-intercepts are: $\left( \sqrt {2} , 0 \right) \mbox { and } \left( - \sqrt {2} , 0 \right)$

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