pre calc help!!!!!

Question

If you were to use completing the square on this problem, x2+4x ____−5=2 what number would go in the blank ?

A)	- 2
B)	- 4
C)	+ 2
D)	+ 4

Answer 1

If the coefficient of x^2 is one, (it is)

then just take the coefficient of x (which is 4)

divide by 2 (4/2 = 2)

and square it to get 4 (2^2 = 4).

NOTES:

If you add 4 to the left side of the equation,

you must also add it to the right side.

The reason we complete the square

is to help us solve for x

by getting the equation in the form:

(x - c)^2 = n

x - c = +/- sqrt(n)

x = c +/- sqrt(n)

So, completing the square

to solve for x in the given equation,

do this:

x^2 + 4x + ____ - 5 = 2

x^2 + 4x + ____ = 7

x^2 + 4x + 4 = 11

(x + 2)^2 = 11

x + 2 = +/- sqrt(11)

x = -2 +/- sqrt(7)

x = -2 + sqrt(11) OR x = -2 - sqrt(11)

Answer 2

D) +4 (half the coefficient of 4x squared)