a)
\(3x\left(5x^2+2x-1\right)\\ =15x^3+6x^2-3x\)
b)
\(\left(x+1\right)\left(x-2\right)\\ =x^2-2x+x-2\\ =x^2-x-2\)
c)
\(-8x^3y^2:2xy\\ =-4x^2y\)
d)
\(\left(5x^4-3x^3+x^2\right):3x^2\\ =\dfrac{5}{3}x^2-x+\dfrac{1}{3}\)
\(a,3x\left(5x^2+2x-1\right)=15x^3+6x^2-3x\)
\(b,\left(x+1\right)\left(x-2\right)=x^2-2x+x-2=x^2-x-2\)
\(c,-8x^3y^2:2xy=-4x^2y\)
\(d,\left(5x^4-3x^3+x^2\right):3x^2=\dfrac{5}{3}x^2-x+\dfrac{1}{3}\)
a) = 3x.5x^2+ 3x.2x - 3x.1 = 15x^3+ 6x^2- 3x
b) =x.x+ 1.x+ x.(-2)+ 1.(-2)= x^2+ x- 2x- 2
c) =-4x^2y
d) =5x^4:3x^2- 3x^3:3x^2+ x^2:3x^2 = 5/3x^2- x+ 1/3
