Question 285082
x-7/(x+4)^2 * x^2-3x-28 / (x-7)^2

x-7 / (x+4)^2 * (x^2-7x+4x-28) / (x-7)^2

(x-7)/(x+4)^2 * (x(x-7)+4(x-7)) /(x-7)^2

(x-7)/(x+4)^2 * (x-7)(x+4)/(x-7)^2

(x-7)(x-7)(x+4)/ (x+4)^2*(x-7)^2

=1/(x+4)