Question

15 Thực hiện phép tính: 

a)\([4x-2\left(x-3\right)].\left(-3x\right)\)      ;     b)\(3[x-3\left(4-2x\right)+8]\)

c)\(5\left(3x^2-4y^3\right)+9\left(2x^2-y^3\right)\)d) \(3x^2\left(2y-1\right)-2x^2\left(5y-3\right)\)

Answer 1

P/s : Phá ngoặc ra là ok : 

a ) 

\(\left[4x-2\left(x-3\right)\right].\left(-3x\right)\)

\(=\left[4x-2x+6\right]\left(-3x\right)\)

\(=-12x^2+6x^2-18x\)

b ) 

\(3\left[x-3\left(4-2x\right)+8\right]\)

\(=3\left[x-12+6x+8\right]\)

\(=3\left[7x-4\right]\)

\(=21x-12\)

c ) 

\(5\left(3x^2-4y^3\right)+9\left(2x^2-y^3\right)\)

\(=15x^2-20y^3+18x^2-9y^3\)

\(=33x^2-29y^3\)

d ) 

\(3x^2\left(2y-1\right)-2x^2\left(5y-3\right)\)

\(=6x^2y-3x^2-10x^2y+6x^2\)

\(=-4x^2y+3x^2\)