SOLUTION: Have to complete the square for these: Let f(x) = 2x^2 + 6x please help!

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Question 948126: Have to complete the square for these:
Let f(x) = 2x^2 + 6x
please help!
Found 2 solutions by josgarithmetic, MathLover1:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
Completing the Square to Solve General Quadratic Equation
http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

f%28x%29+=+2x%5E2+%2B+6x
f%28x%29+=+2%28x%5E2+%2B+3x%29
f%28x%29+=+2%28x%5E2+%2B+3x%2B_%29-2%2A_ ...recall a%5E2%2B2ab%2Bb%5E2=%28a%2Bb%29%5E2, so we have a=1 and we need b and since we have that 2ab=3, then 2%2A1%2Ab=3=>2%2Ab=3b=3%2F2
now square it and add to
f%28x%29+=+2%28x%5E2+%2B+3x%2B%283%2F2%29%5E2%29-2%2A%283%2F2%29%5E2...this 2%2A%283%2F2%29%5E2 we are multiplying by 2 because we have 2 in front of parentheses

f%28x%29+=+2%28x%5E2+%2B+3x%2B%283%2F2%29%5E2%29-2%2A%289%2F4%29
f%28x%29+=+2%28x%5E2+%2B+3x%2B%283%2F2%29%5E2%29-cross%282%29%2A%289%2Fcross%284%292%29
f%28x%29+=+2%28x+%2B3%2F2%29%5E2-9%2F2