Đáp án:
a) \(36{y^2}\)
Giải thích các bước giải:
\(\begin{array}{l}
a){(3y - 5x)^2} - (5x + 3y)(10x - 6y) + {(5x + 3y)^2}\\
= {(5x - 3y)^2} - 2(5x + 3y)(5x - 3y) + {(5x + 3y)^2}\\
= {\left( {5x - 3y - 5x - 3y} \right)^2} = 36{y^2}\\
b)\left( {\dfrac{2}{{x + 1}} - \dfrac{1}{{x - 1}}} \right).\dfrac{{{x^2} - 1}}{{{x^2} - 6x + 9}} - \dfrac{{x - 1}}{{2x - 6}}\\
= \dfrac{{2x - 2 - x - 1}}{{{x^2} - 1}}.\dfrac{{{x^2} - 1}}{{{x^2} - 6x + 9}} - \dfrac{{x - 1}}{{2x - 6}}\\
= \dfrac{{x - 3}}{{{{\left( {x - 3} \right)}^2}}} - \dfrac{{x - 1}}{{2\left( {x - 3} \right)}}\\
= \dfrac{1}{{x - 3}} - \dfrac{{x - 1}}{{2\left( {x - 3} \right)}}\\
= \dfrac{{2 - x + 1}}{{2\left( {x - 3} \right)}} = \dfrac{{3 - x}}{{2\left( {x - 3} \right)}} = - \dfrac{1}{2}
\end{array}\)
