Trắc nghiệm Toán 8: Qui đồng mẫu thức nhiều phân thức có lời giải chi tiết

A. $x(x^2-1)$

B. $x{\left(x-1\right)}^2$

C. $x^2-1$

D. x(x - 1)

A. $12x^2{y}^3$

B. $12x^2{y}^4$

C. $6x^3{y}^2$

D. $12x^{4}y$

A. ${\left(x-y\right)}^2$

B. x - y

C. $3{\left(x-y\right)}^2$

D. $3{\left(x-y\right)}^3$

A. ${\left(x+3\right)}^3$

B. $3{\left(x+3\right)}^2$

C. $3{\left(x+3\right)}^3$

D. ${\left(x+3\right)}^4$

A. $\left(x-2\right){\left(x+2\right)}^2$

B. $(2-x){\left(x-2\right)}^2{\left(x+2\right)}^2$

C. ${\left(x-2\right)}^2{\left(x+2\right)}^2$

D. ${\left(x-2\right)}^2$

A. $4{\left(x+3\right)}^2$

B. 4(x - 3)(x + 3)

C. (x - 3)(x + 3)

D. $4{\left(x-3\right)}^2$

A. Mẫu thức chung của các phân thức $\frac{\text{x}+\text{2}}{\text{5(x}-\text{2)(x}+\text{3)}}\text{,}\frac{\text{1}}{\text{x(x}+\text{3)}}$ là 5x(x - 2)(x + 3)?

B. Mẫu thức chung của các phân thức $\frac{\text{1}}{{\text{2x}}^{\text{2}}\text{y}}\text{,}\frac{\text{1}}{{\text{3xy}}^{\text{3}}}\text{,}\frac{\text{1}}{\text{6y}}$ là $6x^2{y}^3$ .

C. Mẫu thức chung của các phân thức $\frac{\text{x}+\text{1}}{\text{x}-\text{1}}\text{,}\frac{\text{1}}{\text{x}+\text{1}}\text{,}\frac{\text{x}-\text{2}}{{\text{x}}^{\text{2}}-\text{1}}$ là $x^2-1$ .

D. Mẫu thức chung của các phân thức $\frac{\text{x}}{{\text{(x}-\text{2)}}^{\text{2}}}\text{,}\frac{\text{5}}{{\text{(x}+\text{2)}}^{\text{2}}}\text{,}\frac{\text{x}+\text{1}}{{\text{(x}-\text{2)}}^{\text{3}}}$ là ${(x+2)}^2{(x-2)}^2$ .

A. Mẫu thức chung của các phân thức $\frac{\text{2}-\text{a}}{\text{3a}}\text{;}\frac{\text{1}}{\text{4}}$ là 12a.

B. Mẫu thức chung của các phân thức $\frac{\text{1}}{\text{6a}}\text{;}\frac{\text{4a}+\text{1}}{\text{18ab}}\text{;}\frac{\text{10a}}{\text{9b}}$ là 18ab.

C. Mẫu thức chung của các phân thức $\frac{\text{1}}{{\text{x}}^{\text{2}}+\text{2x}+\text{1}}\text{;}\frac{\text{1}}{{\text{x}}^{\text{2}}-\text{1}}$ là $(x^2-1)(x-1)$ .

D. Mẫu thức chung của các phân thức $\frac{\text{1}}{{\text{(x}-\text{2y)}}^{\text{2}}}\text{;}\frac{\text{5x}}{{\text{(x}-\text{2y)}}^{\text{4}}}\text{;}\frac{\text{1}}{\text{3x}}$ là $3x{\left(x-2y\right)}^4$ .

A. $\frac{\text{1}}{\text{3(x}-\text{1)}}\text{;}\frac{\text{x}}{{\text{(x}-\text{2)}}^{\text{2}}}\text{;}\frac{\text{5}}{\text{4(x}-\text{2)}}$

B. $\frac{\text{x}}{\text{x}-\text{1}}\text{;}\frac{\text{5}}{\text{6(x}-{\text{2)}}^{\text{3}}}$

C. $\frac{\text{1}}{{\text{x}}^{\text{2}}-\text{4}}\text{;}\frac{\text{7}}{\text{12(x}-\text{1)}}$

D. $\frac{\text{1}}{\text{x}-\text{2}}\text{;}\frac{\text{5}}{\text{3(x}-{\text{2)}}^{\text{3}}}\text{;}\frac{\text{x}}{\text{5(x}-\text{1)}}$

A. $\frac{\text{1}}{{\text{x}}^{\text{2}}+\text{xy}}\text{;}\frac{\text{1}}{\text{xy}-{\text{y}}^{\text{2}}}\text{;}\frac{\text{3}}{{\text{y}}^{\text{2}}-{\text{x}}^{\text{2}}}$

B. $\frac{\text{1}}{{\text{x}}^{\text{2}}-{\text{y}}^{\text{2}}}\text{;}\frac{\text{6x}}{\text{2x}-\text{2y}}$

C. $\frac{\text{8y}}{{\text{(x}-\text{y)}}^{\text{2}}}\text{;}\frac{\text{7}}{\text{x}+\text{y}}\text{;}\frac{\text{1}}{{\text{y}}^{\text{2}}}$

D. $\frac{\text{4}}{\text{5(x}-\text{y)}}\text{;}\frac{\text{6}}{\text{3x}+\text{3y}}\text{;}\frac{\text{5}}{{\text{x}}^{\text{2}}-{\text{y}}^{\text{2}}}$

A. $\frac{\text{x}-\text{2}}{\text{3(x}-\text{1)}}=\frac{\text{2(x}-\text{2)(x}+\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{5}}{\text{2(x}+\text{1)}}=\frac{\text{5(x}+\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{x}+\text{3}}{{\text{x}}^{\text{2}}-\text{1}}=\frac{\text{2(x}+\text{3)}}{{\text{6(x}}^{\text{2}}-\text{1)}}$

B. $\frac{\text{x}-\text{2}}{\text{3(x}-\text{1)}}=\frac{\text{2(x}-\text{2)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{5}}{\text{2(x}+\text{1)}}=\frac{\text{15(x}-\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{x}+\text{3}}{{\text{x}}^{\text{2}}-\text{1}}=\frac{\text{6(x}+\text{3)}}{{\text{6(x}}^{\text{2}}-\text{1)}}$

C. $\frac{\text{x}-\text{2}}{\text{3(x}-\text{1)}}=\frac{\text{2(x}-\text{2)(x}+\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{5}}{\text{2(x}+\text{1)}}=\frac{\text{15(x}-\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{x}+\text{3}}{{\text{x}}^{\text{2}}-\text{1}}=\frac{\text{6}}{{\text{6(x}}^{\text{2}}-\text{1)}}$

D. $\frac{\text{x}-\text{2}}{\text{3(x}-\text{1)}}=\frac{\text{2(x}-\text{2)(x}+\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{5}}{\text{2(x}+\text{1)}}=\frac{\text{15(x}-\text{1)}}{{\text{6(x}}^{\text{2}}-\text{1)}}\text{,}\frac{\text{x}+\text{3}}{{\text{x}}^{\text{2}}-\text{1}}=\frac{\text{6(x}+\text{3)}}{{\text{6(x}}^{\text{2}}-\text{1)}}$

A. $\frac{\text{1}}{{\text{x}}^{\text{3}}+\text{1}}\text{;}\frac{{\text{x}}^{\text{2}}-\text{x}+\text{1}}{{\text{3(x}}^{\text{3}}+\text{1)}}\text{;}\frac{{\text{x}}^{\text{2}}+\text{x}}{{\text{2(x}}^{\text{3}}+\text{1)}}$

B. $\frac{\text{1}}{{\text{6(x}}^{\text{3}}+\text{1)}}\text{;}\frac{{\text{x}}^{\text{2}}-\text{x}+\text{1}}{{\text{3(x}}^{\text{3}}+\text{1)}}\text{;}\frac{{\text{3x}}^{\text{2}}+\text{3x}}{{\text{6(x}}^{\text{3}}+\text{1)}}$

C. $\frac{\text{6}}{{\text{6(x}}^{\text{3}}+\text{1)}}\text{;}\frac{{\text{4x}}^{\text{2}}-\text{4x}+\text{4}}{{\text{6(x}}^{\text{3}}+\text{1)}}\text{;}\frac{{\text{3x}}^{\text{2}}+\text{3x}}{{\text{6(x}}^{\text{3}}+\text{1)}}$

D. $\frac{{\text{3x}}^{\text{2}}+\text{3x}}{{\text{6(x}}^{\text{3}}+\text{1)}}\text{;}\frac{{\text{4x}}^{\text{2}}-\text{4x}+\text{4}}{{\text{6(x}}^{\text{3}}+\text{1)}}\text{;}\frac{\text{6}}{{\text{6(x}}^{\text{3}}+\text{1)}}$

A. $\frac{\text{1}}{\text{xy}}=\frac{\text{z}}{\text{xyz}}\text{,}\frac{\text{1}}{\text{yz}}=\frac{\text{x}}{\text{xyz}}\text{,}\frac{\text{3}}{\text{xz}}=\frac{\text{3}}{\text{xyz}}$

B. $\frac{\text{1}}{\text{xy}}=\frac{\text{z}}{\text{xyz}}\text{,}\frac{\text{1}}{\text{yz}}=\frac{\text{x}}{\text{xyz}}\text{,}\frac{\text{3}}{\text{xz}}=\frac{\text{3y}}{\text{xyz}}$

C. $\frac{\text{1}}{\text{xy}}=\frac{\text{z}}{\text{xyz}}\text{,}\frac{\text{1}}{\text{yz}}=\frac{\text{1}}{\text{xyz}}\text{,}\frac{\text{3}}{\text{xz}}=\frac{\text{3y}}{\text{xyz}}$

D. $\frac{\text{1}}{\text{xy}}=\frac{\text{1}}{\text{xyz}}\text{,}\frac{\text{1}}{\text{yz}}=\frac{\text{x}}{\text{xyz}}\text{,}\frac{\text{3}}{\text{xz}}=\frac{\text{3y}}{\text{xyz}}$

A. $\frac{3}{5x^{2}yz}=\frac{12yz}{20x^2{y}^2{z}^2};\frac{5}{4y^{2}z}=\frac{25x^{2}z}{20x^2{y}^2{z}^2};\frac{6}{x{z}^2}=\frac{120x{y}^2}{20x^2{y}^2{z}^2}$

B. $\frac{\text{3}}{{\text{5x}}^{\text{2}}\text{yz}}=\frac{\text{12yz}}{{\text{20x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}\text{;}\frac{\text{5}}{{\text{4y}}^{\text{2}}\text{z}}=\frac{{\text{25x}}^{\text{2}}\text{z}}{{\text{20x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}\text{;}\frac{\text{6}}{{\text{xz}}^{\text{2}}}=\frac{{\text{x}}^{\text{2}}\text{y}}{{\text{20x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}$

C. $\frac{\text{3}}{{\text{5x}}^{\text{2}}\text{yz}}=\frac{\text{3yz}}{{\text{x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}\text{;}\frac{\text{5}}{{\text{4y}}^{\text{2}}\text{z}}=\frac{{\text{5x}}^{\text{2}}\text{z}}{{\text{x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}\text{;}\frac{\text{6}}{{\text{xz}}^{\text{2}}}=\frac{{\text{x}}^{\text{2}}\text{y}}{{\text{x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}$

D. $\frac{\text{3}}{{\text{5x}}^{\text{2}}\text{yz}}=\frac{\text{3yz}}{{\text{20x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}\text{;}\frac{\text{5}}{{\text{4y}}^{\text{2}}\text{z}}=\frac{{\text{20x}}^{\text{2}}\text{z}}{{\text{20x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}\text{;}\frac{\text{6}}{{\text{xz}}^{\text{2}}}=\frac{{\text{120x}}^{\text{2}}\text{y}}{{\text{20x}}^{\text{2}}{\text{y}}^{\text{2}}{\text{z}}^{\text{2}}}$

A. 4x; x + 2

B. 2x; x + 2

C. 4x; x + 1

D. $4x^2;x+2$