Verified answer

you can factor

x^2 + 12x - 64 = 0

(x + 16)(x - 4) = 0

x = {-16, 4}

you can complete the square

x^2 + 12x = 64

x^2 + 12x + 36 = 64 + 36

(x + 6)^2 = 100

x + 6 = ± 10

x = -6 ± 10

x = {-16, 4}

you can use the quadratic formula

(-12 ± √400) / 2

(-12 ± 20) / 2

-6 ± 10

x = {-16, 4}

the stairs you have given us are unnecessarily complicated. bypass over step b and for c use a million/2 the x coefficient x^2+12x= sixty 4 x^2+12x+36 = a hundred (x+6)^2 = a hundred x+6 = ± 10 x = -6 + 10 = 4 x = -6 -10 = -sixteen

wow... I used to do these blindfolded at school! I'm shocked at myself that I forgot it all!

Hope some one has the answer!