Write the quadratic function f(x) = x^2 + 8x + 3 in vertex form?

Question

A) f(x) = (x - 4)^2 - 13

B) f(x) = (x - 4)^2 + 3

C) f(x) = (x + 4)^2 + 3

D) f(x) = (x + 4)^2 - 13

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Answer 1 · 2018-03-27T20:33:27

you have to complete the square.

#x^2+8x+3#

first you have to open a bracket and put the #x#
into it add up to half of the term b which is #8x# and square it.

#(x+(8x)/2)^2#

#(x+4x)^2#

always completing the square, the sign after the brackets is negative. Then you have to half again the term b and square it.

#(x+4x)^2-4^2#

And finally you have to add the term c which is 3 in this case.
#(x+4x)^2-4^2+3#

Simplify
#(x+4x)^2-16-3#

Answer
#(x+4x)^2-13#

vertex is (-4,-13)