Question

Tính

c. ( - 4xy ) . ( 2xy² - 3x²y )

f. ( - 5x ) . ( 3x³ + 7x² - x )

g. ( 1/2 a³b²  -  3/4 ab⁴ ) ( 4/3 a³b )

Answer 1

`c)`\(\left(-4xy\right)\left(2xy^2-3x^2y\right)=-8x^2y^3+12x^3y^2\)

`f)`\(\left(-5x\right)\left(3x^3+7x^2-x\right)=-15x^4-35x^3+5x^2\)

`g)`\(\left(\dfrac{1}{2}a^3b^2-\dfrac{3}{4}ab^4\right)\left(\dfrac{4}{3}a^3b\right)=\dfrac{2}{3}a^6b^3-a^4b^5\)

Answer 2

\(c=\left(-4xy.2xy^2\right)-\left(-4xy.3x^2y\right)=-8x^2y^3-\left(-12x^3y^2\right)=-8x^2y^3+12x^3y^2\)

\(f=\left(-5x.3x^3\right)+\left(-5x.7x^2\right)-\left(-5x.x\right)=\left(-15x^4\right)+\left(-35x^3\right)-\left(-5x^2\right)\\ =-15x^4-35x^3+5x^2\)

\(g=\left(\dfrac{1}{2}a^3b^2.\dfrac{4}{3}a^3b\right)-\left(\dfrac{3}{4}ab^4.\dfrac{4}{3}a^3b\right)=\dfrac{2}{3}a^6b^3-a^4b^5\)