Question

Rút gọn phân tử :

\(\frac{\left(a-b\right)\left(c-d\right)}{\left(b^2-a^2\right)\left(d^2-c^2\right)}\)

Answer 1

Ta thấy: \(\frac{\left(a-b\right)\left(c-d\right)}{\left(b^2-a^2\right)\left(d^2-c^2\right)}=\frac{\left(b-a\right)\left(d-c\right)}{\left(b-a\right)\left(b+a\right)\left(d-c\right)\left(d+c\right)}=\frac{1}{\left(a+b\right)\left(c+d\right)}\)

Answer 2

\(\frac{\left(a-b\right)\left(c-d\right)}{\left(b^2-a^2\right)\left(d^2-c^2\right)}\)

\(=\frac{\left(a-b\right)\left(c-d\right)}{\left(b-a\right)\left(b+a\right)\left(d-c\right)\left(d+c\right)}\)

\(\frac{1}{\left(a+b\right)\left(c+d\right)}\)