Find x-intercept and y-intercept for the function: f(x)=9x^2+12x+4.

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Offline malylo

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Look at the function: f(x)=9x^2+12x+4. Please find x-intercept and y-intercept.


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« Last Edit: 10/11/2011 03:22:34 by JP »

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Offline CliffordK

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y=9x2+12x+4

The Y-intercept is easy to calculate.  Just set X=0.

y=9*02+12*0+4 = 4

To  calculate the X-intercept, it is easiest to first factor the quadratic, in this case it is relatively easy, a perfect square.
 
y=(3x+2)(3x+2)

Now, set Y=0.

0=(3x+2)(3x+2)

So, either half (which is the same) must equal zero.

0=3x+2

3x=-2

x=-2/3