\(a,\)
\(A=\dfrac{x^2-2x}{x^2+x-6}.\dfrac{x^2-9}{x^2-3x}\)
\(A=\dfrac{x\left(x-2\right)}{\left(x+3\right)\left(x-2\right)}.\dfrac{\left(x-3\right)\left(x+3\right)}{x\left(x-3\right)}\)
\(A=\dfrac{x}{\left(x+3\right)}.\dfrac{\left(x+3\right)}{x}=1\)
\(b,\)
\(B=\dfrac{2x^2+5x-3}{x^2-9}.\dfrac{4x^2-1}{x^2-6x+9}\)
\(B=\dfrac{\left(x+3\right)\left(2x-1\right)}{\left(x-3\right)\left(x+3\right)}.\dfrac{\left(2x-1\right)\left(2x+1\right)}{\left(x-3\right)^2}\)
\(B=\dfrac{\left(2x-1\right)}{\left(x-3\right)}.\dfrac{\left(2x-1\right)\left(2x+1\right)}{\left(x-3\right)^2}\)
\(B=\dfrac{\left(2x-1\right)^2.\left(2x+1\right)}{\left(x-3\right)^3}\)
