Question

calcule a soma:
$\frac{y-1}{y+1} + \frac{y+1}{y-1}= \frac{4y}{ y^{2}-1 }$

Answer 1

(y -1)(y - 1) + (y + 1)(y + 1) = 4y

y² - 2y + 1 + y² + 2y + 1 - 4y = 0

2y²  - 4y + 2

2(y²  - 2y + 1) ==> 2(y - 1)²