X^2-8x+ _ =-1+_?

what do you have to add in order to complete the square

Hello from MrBillDoesMath!

_ =  (-4) ^2      (Which equals 16)

Discussion:

Generally

(x + a) ^ 2 = x^2 + 2ax + a^2

Note that the constant term in this perfect square equals the square of (1/2) the coefficient of x. Applying the fact to your equation, gives

x^2 - 8x + _ = -1 + _                    => -8/2  =  -4

x^2 - 8x + (-4)^2 = -1 + (-4)^2   =>

(x -4)^2             = - 1 + 16 = 15    =>

(x-4)^2 = 15                                 =>

x-4 = +\- sqrt(15)                        =>

x = 4 +\- sqrt(15)

Thank you,

MrB

answer is the third choice:

3x^5+4x^4+x^3+2x^2-10x-7=0

step-by-step explanation: