Bài 36 :
a) \(\dfrac{1}{x+2}=\dfrac{1}{x+2};\dfrac{2}{2x+4}=\dfrac{2}{2\left(x+2\right)}=\dfrac{1}{x+2};\dfrac{3}{3x+6}=\dfrac{3}{3\left(x+2\right)}=\dfrac{1}{x+2}\)
b) \(\dfrac{1}{x+3}=\dfrac{x-3}{\left(x+3\right)\left(x-3\right)}\)
\(\dfrac{2}{2x-6}=\dfrac{2}{2\left(x-3\right)}=\dfrac{1}{x-3}=\dfrac{x+3}{\left(x+3\right)\left(x-3\right)}\)
\(\dfrac{3}{3x-9}=\dfrac{3}{3\left(x-3\right)}=\dfrac{1}{x-3}=\dfrac{x+3}{\left(x+3\right)\left(x-3\right)}\)
c) \(\dfrac{1}{x^2-4}=\dfrac{1}{x^2-4}\)
\(\dfrac{2}{x+2}=\dfrac{2\left(x-2\right)}{\left(x+2\right)\left(x-2\right)}=\dfrac{2x-4}{x^2-4}\)
\(\dfrac{3}{x-2}=\dfrac{3\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{3x+6}{x^2-4}\)
d) \(\dfrac{1}{x}=\dfrac{1}{x\left(x+2\right)}\)
\(\dfrac{2}{x+2}=\dfrac{2x}{x\left(x+2\right)}\)
\(\dfrac{3}{x\left(x+2\right)}=\dfrac{3}{x\left(x+2\right)}\)
\(Bài.37:\\ d,x^2-5x+6=\left(x-2\right)\left(x-3\right)\\ MC:\left(x-3\right)\left(x-2\right)\\ Ta.có:\dfrac{2}{x^2-5x+6}=\dfrac{2}{\left(x-3\right)\left(x-2\right)};\dfrac{3}{x-3}=\dfrac{3\left(x-2\right)}{\left(x-3\right)\left(x-2\right)}=\dfrac{3x-6}{\left(x-3\right)\left(x-2\right)}\\ ---\\ e,x^2-3x+2=\left(x-2\right)\left(x-1\right)\\x^2-x=x\left(x-1\right)\\ MC:x\left(x-2\right)\left(x-1\right)\\ Ta.có:\dfrac{4}{x^2-3x+2}=\dfrac{4}{\left(x-2\right)\left(x-1\right)}=\dfrac{4x}{x.\left(x-2\right)\left(x-1\right)}\\ \dfrac{1}{x^2-x}=\dfrac{1}{x\left(x-1\right)}=\dfrac{x-2}{x\left(x-2\right)\left(x-1\right)}\)
\(a,MSC:xy^2\\ Ta.có:\dfrac{5}{xy}=\dfrac{5y}{5xy^2};\dfrac{1}{xy^2}=\dfrac{1}{xy^2}\\ b,MSC:x\left(x-1\right)\\ Ta.có:\dfrac{1}{x^2-x}=\dfrac{1}{x\left(x-1\right)};\dfrac{2}{x-1}=\dfrac{2x}{x\left(x-1\right)}\\ c,MSC:x\left(x+2\right)\left(x-2\right)\\ Ta.có:\dfrac{x^2-4}{x^2+2x}=\dfrac{x^2-4}{x\left(x+2\right)}=\dfrac{\left(x-2\right)^2\left(x+2\right)}{x\left(x+2\right)\left(x-2\right)}\\ \dfrac{x}{x-2}=\dfrac{x.x\left(x+2\right)}{x.\left(x-2\right)\left(x+2\right)}=\dfrac{x^2\left(x+2\right)}{x\left(x-2\right)\left(x+2\right)}\left(Đ.S.đề.sai\right)\)
