Question 75570
Since we're looking for f(x)=0, we're looking for y=0 since y and f(x) can be interchanged. In other words, we are looking for the x-intercept, since y=0 for all x-intercepts. So we substitute 0 in for f(x) and we get:

{{{0=3x-12}}} Now we solve for x
{{{0+12=3x+cross(-12+12)}}} Add 12 to both sides
{{{12/3=cross(3/3)x}}} Divide both sides by 3. This will isolate x.
{{{x=4}}}

So if we let x=4 we should get f(x)=0, in other words, f(4)=0. So lets verify this:

<p>
Check:
{{{f(x)=3x-12}}}
{{{f(4)=3(4)-12}}} Plug in x=4
{{{f(4)=12-12}}}
{{{f(4)=0}}}      works
This verifies our answer
{{{ graph( 300, 200, -6, 5, -10, 10, 3x-12) }}}Here you can see the graph of {{{y=3x-12}}} and the x-intercept of (4,0)