Rút gọn biểu thức
a) \(A=\dfrac{x+3}{2x^2+6x}\)
\(A=\dfrac{1.\left(x+3\right)}{2x\left(x+3\right)}\)
\(A=\dfrac{1}{2x}\)
b) \(B=\dfrac{2x-9}{x-6}+\dfrac{2-x}{x-6}-\dfrac{1}{6-x}\)
\(B=\dfrac{2x-9}{x-6}+\dfrac{2-x}{x-6}+\dfrac{1}{x-6}\)
\(B=\dfrac{2x-9+2-x+1}{x-6}\)
\(B=\dfrac{x-6}{x-6}\)
\(B=1\)