SOLUTION: Find the Zeros of the function. f(x)=3x^2-7x-13 Here is what i have tried.. 3x^2-(7x/2)^2=13 but then i get a decimal and when i go to factor it it is extremely hard to f

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find the Zeros of the function. f(x)=3x^2-7x-13 Here is what i have tried.. 3x^2-(7x/2)^2=13 but then i get a decimal and when i go to factor it it is extremely hard to f      Log On


   

Question 910527: Find the Zeros of the function.
f(x)=3x^2-7x-13
Here is what i have tried..
3x^2-(7x/2)^2=13
but then i get a decimal and when i go to factor it it is extremely hard to find that.. Am i suppose to divide by 3 first before i use this way my teacher taught me? Or am i to use the quadratic equation? please advise, thank you for your help.
Found 2 solutions by ewatrrr, richwmiller:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
f(x)=3x^2-7x-13
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 3x%5E2%2B-7x%2B-13+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-7%29%5E2-4%2A3%2A-13=205.

Discriminant d=205 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--7%2B-sqrt%28+205+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-7%29%2Bsqrt%28+205+%29%29%2F2%5C3+=+3.55297017721273
x%5B2%5D+=+%28-%28-7%29-sqrt%28+205+%29%29%2F2%5C3+=+-1.21963684387939

Quadratic expression 3x%5E2%2B-7x%2B-13 can be factored:
3x%5E2%2B-7x%2B-13+=+3%28x-3.55297017721273%29%2A%28x--1.21963684387939%29
Again, the answer is: 3.55297017721273, -1.21963684387939. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+3%2Ax%5E2%2B-7%2Ax%2B-13+%29

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
It looks like you are trying to complete the square. Yes. Divide by 3 first.