Đáp án:
b) 1
Giải thích các bước giải:
\(\begin{array}{l}
B1:\\
a){x^2} + 6x - 7 - {x^2} + 3x = 9x - 7\\
b)\dfrac{{3x + 1 - 2x - 6}}{{x - 5}} = \dfrac{{x - 5}}{{x - 5}} = 1\\
c)\dfrac{{30x}}{{\left( {3x - 1} \right)\left( {3x + 1} \right)}} + \dfrac{4}{{3x - 1}} - \dfrac{5}{{3x + 1}}\\
= \dfrac{{30x + 4\left( {3x + 1} \right) - 5\left( {3x + 1} \right)}}{{\left( {3x - 1} \right)\left( {3x + 1} \right)}}\\
= \dfrac{{30x + 12x + 4 - 15x - 5}}{{\left( {3x - 1} \right)\left( {3x + 1} \right)}}\\
= \dfrac{{27x - 1}}{{\left( {3x - 1} \right)\left( {3x + 1} \right)}}
\end{array}\)
