SOLUTION: How do i solve "If f(2)=0 and f(x)=3x^2+kx-4,find k" i need help solving this step by step.

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Question 451555: How do i solve "If f(2)=0 and f(x)=3x^2+kx-4,find k" i need help solving this step by step.
Found 2 solutions by robertb, tinbar:
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
f%282%29+=+3%2A2%5E2+%2B+k%2A2+-+4+=+0
==> 12+%2B+2k+-+4+=+0
==> 2k + 8 = 0
==> 2k = -8
==> k = -4.

Answer by tinbar(133) About Me  (Show Source):
You can put this solution on YOUR website!
well, you know that f(2)=0, so let's find f(2) by actually plugging x=2 in the given function f(x)=3x^2+kx-4.
f(2)=3(2^2)+k(2)-4=8+2k
remember that f(2)=0, so we need to set 8+2k equal to 0 since they are both the same f(2)
8+2k=0
2k=-8
k=-4