Question

What value of $k$ will make $4x^2 - 20x + k$ the square of a binomial?

Answer 1

Answer:

k = 25

Step-by-step explanation:

(2x  - sqrt(k) )^2              Expand this as a binomial                          

4x^2 - 4x*sqrt(k) + k      The middle term must be -20x Solve for k so it is

-4xsqrt(k) = - 20x            Divide by -4x

sqrt(k) = -20x/-4x             Do the division

sqrt(k) = 5                         Square both sides

k = 25