Question

Сократите дробь (x−3)2 / x2+2x−15.

Answer 1

(x-3)²/x²+2x-15

x²+2x+15 = 0

Теорема Виета:

{x1+x2 = -2

{x1•x2 = 15

x1 = -5

x2 = 3

x²+2x+15 = (x+5)(x-3)

(x-3)²/(x+5)(x-3) = x-3/x+5

Answer 2

$\displaystyle \tt \frac{(x-3)^2}{x^2+2x-15}=\frac{(x-3)^2}{x^2+5x-3x-15}=\frac{(x-3)^2}{x(x+5)-3(x+5)}=\\\\ \displaystyle \tt =\frac{(x-3)^2}{(x+5)(x-3)}=\bold{\frac{x-3}{x+5}}$