Question

bài 2 quy đồng các mẫu sau 

a,\(\dfrac{3x}{2x+4}và\dfrac{x+3}{x^2-4}\)

b,\(\dfrac{1}{x+2}và\dfrac{8}{2x-x^2}\)

c,\(\dfrac{2x}{x^2-8x+16}và\dfrac{x}{3x^2-12x}\)

d,\(\dfrac{x+5}{x^2+4x+4}và\dfrac{x}{3x+6}\)

e,\(\dfrac{2x+6}{x^3-9x}và\dfrac{1}{x^2-5x+6}\)

 

Answer 1

a)MCNN : 2(x+2)(x-2)

 \(\dfrac{3x}{2x+4}=\dfrac{3x}{2\left(x+2\right)}=\dfrac{3x\left(x-2\right)}{2\left(x-2\right)\left(x+2\right)};\dfrac{x+3}{x^2-4}=\dfrac{2\left(x+3\right)}{2\left(x-2\right)\left(x+2\right)}\)

Answer 2

b) \(MCNN:x\left(x-2\right)\left(x+2\right)\)

\(\dfrac{1}{x+2}=\dfrac{x\left(x-2\right)}{x\left(x+2\right)\left(x-2\right)}\)

\(\dfrac{8}{2x-x^2}=\dfrac{8\left(x+2\right)}{x\left(x+2\right)\left(2-x\right)}=-\dfrac{8\left(x+2\right)}{x\left(x+2\right)\left(x-2\right)}\)

Answer 3

\(c.MCNN:3x\left(x-4\right)^2\)

\(\dfrac{2x}{x^2-8x+16}=\dfrac{2x.3x}{3x.\left(x-4\right)^2}=\dfrac{6x^2}{3x\left(x-4\right)^2}\)

\(\dfrac{x}{3x^2-12x}=\dfrac{x}{3x\left(x-4\right)}=\dfrac{x\left(x-4\right)}{3x\left(x-4\right)^2}\)

Answer 4

d.\(MCNN:3\left(x+2\right)^2\)

\(\dfrac{x+5}{x^2+4x+4}=\dfrac{3\left(x+5\right)}{3\left(x+2\right)^2}\)

\(\dfrac{x}{3x+6}=\dfrac{x\left(x+2\right)}{3\left(x+2\right)^2}\)

Answer 5

e.\(MCNN:x\left(x-3\right)\left(x+3\right)\left(x-2\right)\)

\(\dfrac{2x+6}{x^3-9x}=\dfrac{2\left(x+3\right)}{x\left(x^2-9\right)}=\dfrac{2\left(x+3\right)\left(x-2\right)}{x\left(x+3\right)\left(x-3\right)\left(x-2\right)}\)

\(\dfrac{1}{x^2-5x+6}=\dfrac{1}{\left(x-2\right)\left(x-3\right)}=\dfrac{x\left(x+3\right)}{x\left(x+3\right)\left(x-3\right)\left(x-2\right)}\)