Question

Tính .

\(\dfrac{b}{ab-5a^2}-\dfrac{15b-25a}{b^2-25a^2}\)

Answer 1

\(\dfrac{b}{ab-5a^2}-\dfrac{15b-25a}{b^2-25a^2}\)

\(=\dfrac{b}{a.\left(b-5a\right)}-\dfrac{5.\left(3b-5a\right)}{\left(b-5a\right).\left(b+5a\right)}\)

\(=\dfrac{b.\left(b+5a\right)-5a.\left(3b-5a\right)}{a.\left(b-5a\right).\left(b+5a\right)}\)

\(=\dfrac{b^2+5ab-15ab+25a^2}{a.\left(b-5a\right).\left(b+5a\right)}\)

\(=\dfrac{b^2-10ab+25a^2}{a.\left(b-5a\right).\left(b+5a\right)}\)

\(=\dfrac{\left(b-5a\right)^2}{a.\left(b-5a\right).\left(b+5a\right)}\)

\(=\dfrac{b-5a}{a.\left(b+5a\right)}\)

Answer 2

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