Question

Giúp mk tiếp nha m.n! Thanks nhiều!

Tính

a, \(3x\left(x^2-2x\right)\)

b, \(\left(27x^3-1\right)\)\(\div\)\(\left(9x^2+3x+1\right)\)

c,\(\dfrac{4y^3}{7x^2}\)\(\times\)\(\dfrac{14x^3}{y}\)

d, \(\dfrac{x^2-9}{2x+6}\)\(\div\)\(\dfrac{3-x}{2}\)

Answer 1

a)\(3x\left(x^2-2x\right)\)

\(=3x^3-6x^2\)

b) \(\left(27x^3-1\right):\left(9x^2+3x+1\right)\)

\(=\left(3x-1\right)\left(9x^2+3x+1\right):\left(9x^2+3x+1\right)\)

\(=3x-1\)

c) \(\dfrac{4y^3}{7x^2}.\dfrac{14x^3}{y}\)

\(=8xy^2\)

\(\)d)\(\dfrac{x^2-9}{2x+6}:\dfrac{3-x}{2}\)

\(=-\dfrac{\left(x-3\right)\left(x+3\right)}{2\left(x+3\right)}:\dfrac{x-3}{2}\)

\(=-\dfrac{\left(x+3\right)\left(x-3\right)}{2\left(x+3\right)}.\dfrac{2}{\left(x-3\right)}\)

\(=-1\)

Answer 2

a.3x(x²-2x)=3x³-6x²

b.(27x³-1) : (9x²+3x+1)=\([\left(3x\right)^3-1]:\left(9x^2+3x+1\right)=\left(3x-1\right)\left(9x^2+3x+1\right):\left(9x^2+3x+1\right)=3x-1\)