\(a,\dfrac{7x-1}{2x^2+6x}=\dfrac{\left(7x-1\right)\left(x-3\right)}{2x\left(x+3\right)\left(x-3\right)}=\dfrac{7x^2-22x+3}{2x\left(x-3\right)\left(x+3\right)}\\ \dfrac{5-3x}{x^2-9}=\dfrac{2x\left(5-3x\right)}{2x\left(x-3\right)\left(x+3\right)}=\dfrac{10x-6x^2}{2x\left(x-3\right)\left(x+3\right)}\)

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

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

c) \(=\dfrac{x+1}{x^3+1}=\dfrac{x+1}{\left(x+1\right)\left(x^2+x+1\right)}=\dfrac{1}{x^2+x+1}\)

`a, (3x^2+6xy)/(6x^2) = (x+2y)/(3x)`

`b, (2x^2-x^3)/(x^2-4) = (x^2(2-x))/((x-2)(x+2))`

`= -x^2/(x+2)`

`c, (x+1)/(x^3+1) = 1/(x^2-x+1)`

\(\dfrac{x+1}{4x^2y}=\dfrac{3y\left(x+1\right)}{12x^2y^2}\)

\(\dfrac{y-2}{6xy^2}=\dfrac{2x\left(y-2\right)}{12x^2y^2}\)

a)\(\dfrac{21}{56}\) và \(\dfrac{40}{56}\)

b)\(\dfrac{4}{12}\);\(\dfrac{6}{12}\) và \(\dfrac{10}{12}\)

a) 21/56 và 40/56

b) 4/14, 6/12 và 10/12

câu b là 4/12, 6/12 và 10/12 nha 

Bài 2:

a: \(\dfrac{1}{2x^3y}=\dfrac{6yz^3}{12x^3y^2z^3}\)

\(\dfrac{2}{3xy^2z^3}=\dfrac{2\cdot4x^2}{12x^3y^2z^3}=\dfrac{8x^2}{12x^3y^2z^3}\)

\(a,=\dfrac{5}{10};\dfrac{6}{10};\dfrac{2}{10}\)

\(b,=\dfrac{8}{12};\dfrac{5}{12};\dfrac{9}{12}\)

\(\dfrac{1}{2}=\dfrac{1x5x10}{2x5x10}=\dfrac{50}{100}\)

\(\dfrac{3}{5}=\dfrac{3x2x10}{5x2x10}=\dfrac{60}{100}\)

\(\dfrac{2}{10}=\dfrac{2x2x5}{10x2x5}=\dfrac{20}{100}\)

a) \(\dfrac{1}{2};\dfrac{3}{5};\dfrac{2}{10}\)    b) \(\dfrac{2}{3};\dfrac{5}{12};\dfrac{3}{4}\)

a)\(\dfrac{5}{10};\dfrac{6}{10};\dfrac{2}{10}\) b) \(\dfrac{8}{12};\dfrac{5}{12};\dfrac{9}{12}\)