Tính: a) $5xy^{2}.(-\frac{3}{10}x^{2}y)+\frac{3}{4}x^{3}y^{3}$ b) $\frac{1}{4}x^{4}y.(-\frac{2}{3}x^{3}y^{2})-\frac{1}{3}x^{7}y^{3}$

Đáp án:

Giải thích các bước giải:

$\text{a) 5xy². ($\dfrac{-3}{10}$x²y) + $\dfrac{3}{4}$x³y³}$

$\text{= $\dfrac{-3}{2}$x³y³+ $\dfrac{3}{4}$x³y³}$

$\text{=  ($\dfrac{3}{4}$ + $\dfrac{-3}{2}$).x³y³}$

$\text{= $\dfrac{-3}{4}$x³y³}$

$\text{b) $\dfrac{1}{4}$$x^{4}$y. ( $\dfrac{-2}{3}$x³y²) - $\dfrac{1}{3}$$x^{7}$y³}$

$\text{ = ($\dfrac{-2}{12}$$x^{7}$y³) - $\dfrac{1}{3}$$x^{7}$y³}$

$\text{ = ($\dfrac{-2}{12}$ - $\dfrac{1}{3}$).$x^{7}$y³}$

$\text{ = $\dfrac{-1}{2}$$x^{7}$y³}$

`\color{red}{\text{Nakento}`

Giải thích các bước giải:

`a)`

`5xy^2 . (-3/10x^2y) + 3/4x^3y^3`

`= 5 . (-3/10) . xy^2 . x^2y + 3/4x^3y^3`

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

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

`= x^3y^3 . (-3)/4`

`= (-3)/4x^3y^3`

`b)`

`1/4x^4y . (-2/3x^3y^2) - 1/3x^7y^3`

`= 1/4 . (-2/3) . x^4y . x^3y^2 - 1/3x^7y^3`

`= (-1)/6x^7y^3 - 1/3x^7y^3`

`= x^7y^3((-1)/6 - 1/3)`

`= x^7y^3 . (-1)/2`

`= (-1)/2x^7y^3`