Philip P. answered 11/06/17
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y = x2 +8x + 14
To put the equation into vertex form, we are going to "complete the square" on the right hand side of the equation:
y = (x2 + 8x + C) + 14 - C
We are going to add a number C to the first two terms that complete the square. Since we added C to the RHS, we need to subtract it again so we don't change anything (C - C = 0). The value of C is half of the coefficient of the x term (8) squared, that is C = (8/2)2 = 42 = 16. So our equation is:
y = (x2 + 8x + 16) + 14 - 16 = (x2 + 8x + 16) - 2
Now x2 + 8x + 16 is a perfect square equal to x + half of the coefficient of the x term (8), all squared:
x2 + 8x + 16 = (x + 8/2)2 = (x + 4)2
Our final equation, in vertex form, is:
y = (x+4)2 - 2