Giúp mình với ạ!! Mình cần gấp ạ!!!

`a)`

`A=5x(3x^2 -4x+5)`

`=15x^3 - 20x^2 + 25x`

`b)`

`B=5(x^2 -3x+1) +x(5x+15)+5`

`=5x^2 - 15x+5+5x^2 +15x+5`

`=10x^2 + 10`

`c)`

`A=-3(x+4)(x-7)+7(x-5)(x-1)`

`=(-3x-12)(x-7)+(7x-35)(x-1)`

`=-3x(x-7)-12(x-7)+7x(x-1)-35(x-1)`

`=-3x^2 +21x-12x+84+7x^2 -7x-35x+35`

`=4x^2 -33x+119`

`d)`

`A=4(x-1)(x+1)-(2x+1)(2x-1)`

`=4(x^2 -1)-4x^2 +1`

`=4x^2 -4-4x^2 +1`

`=-3`

`e)`

`A=(x+3)(x^2 +3x-5)`

`=x(x^2 +3x-5)+3(x^2 +3x-5)`

`=x^3 +3x^2 -5x+3x^2 +9x-15`

`=x^3 + 6x^2 + 4x-15`.