a)\(\left(x-3\right)\left(x+3\right)\left(x+2\right)-\left(x-1\right)\left(x^2-3\right)-5x\left(x+4\right)^2-\left(x-5\right)^2\)

\(=\left(x^2-9\right)\left(x+2\right)-\left(x^3-3x-x^2+3\right)-5x\left(x^2+8x+16\right)-\left(x^2-10x+25\right)\)

\(=x^3+2x^2-9x-18-x^3+x^2+3x-3-5x^3-40x^2-80x-x^2+10x-25\)

\(=-5x^3-38x^2-76x-46\)

b)\(2x\left(x-4\right)^2-\left(x+5\right)\left(x-2\right)\left(x+2\right)+2\left(x+5\right)^2-\left(x-1\right)^2\)

\(=2x\left(x^2-8x+16\right)-\left(x+5\right)\left(x^2-4\right)+2\left(x^2+10x+25\right)-\left(x^2-2x+1\right)\)

\(=2x^3-16x^2+32x-\left(x^3+5x^2-4x-20\right)+2x^2+20x+50-x^2+2x-1\)

\(=x^3-20x^2+58x+69\)

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

\(=x^2+10x+25-4x\left(4x^2+12x+9\right)-\left(2x-1\right)\left(x^2-9\right)\)

\(=x^2+10x+25-16x^3-48x^2-36x-\left(2x^3-x^2-18x+9\right)\)

\(=-18x^3-46x^2-8x+16\).

a) Ta có: \(\left(x-3\right)\left(x+3\right)\left(x+2\right)-\left(x-1\right)\left(x^2-3\right)-5x\left(x+4\right)^2-\left(x-5\right)^2\)

\(=\left(x^2-9\right)\left(x+2\right)-\left(x-1\right)\left(x^2-3\right)-5x\left(x^2+8x+16\right)-\left(x^2-10x+25\right)\)

\(=x^3+2x^2-9x-18-\left(x^3-3x-x^2+3\right)-5x^3-40x^2-80x-x^2+10x-25\)

\(=-4x^3-39x^2-79x-43-x^3+3x+x^2-3\)

\(=-5x^3-38x^2-76x-46\)

b) Ta có: \(2x\left(x-4\right)^2-\left(x+5\right)\left(x-2\right)\left(x+2\right)+2\left(x+5\right)^2-\left(x-1\right)^2\)

\(=2x\left(x^2-8x+16\right)-\left(x+5\right)\left(x^2-4\right)+2x^2+20x+50-x^2+2x-1\)

\(=2x^3-16x^2+32x-x^3+4x-5x^2+20+x^2+22x+49\)

\(=x^3-20x^2+56x+49\)

c) Ta có: \(\left(x+5\right)^2-4x\left(2x+3\right)^2-\left(2x-1\right)\left(x-3\right)\left(x+3\right)\)

\(=x^2+10x+25-4x\left(4x^2+12x+9\right)-\left(2x-1\right)\left(x^2-9\right)\)

\(=x^2+10x+25-16x^3+48x-36x-2x^3+18x+x^2-9\)

\(=-18x^3+2x^2+40x+16\)

a, Ta có : \(\left(x-3\right)\left(x+3\right)\left(x+2\right)-\left(x-1\right)\left(x^2-3\right)-5x\left(x+4\right)^2-\left(x-5\right)^2\)

\(=\left(x^2-9\right)\left(x+2\right)-\left(x-1\right)\left(x^2-3\right)-5x\left(x^2+8x+16\right)-\left(x-5\right)^2\)

\(=x^3-9x+2x^2-18-\left(x^3-x^2-3x+3\right)-\left(5x^3+40x^2+80x\right)-\left(x^2-10x+25\right)\)

\(=x^3-9x+2x^2-18-x^3+x^2+3x-3-5x^3-40x^2-80x-x^2+10x-25\)

\(=-5x^3-38x^2-76x-46\)

\(b,\) Ta có : \(2x\left(x-4\right)^2-\left(x+5\right)\left(x-2\right)\left(x+2\right)+2\left(x+5\right)^2-\left(x-1\right)^2\)

\(=2x\left(x-4\right)^2-\left(x+5\right)\left(x^2-4\right)+2\left(x+5\right)^2-\left(x-1\right)^2\)

\(=2x\left(x^2-8x+16\right)-\left(x^3+5x^2-4x-20\right)+2\left(x^2+10x+25\right)-\left(x^2-2x+1\right)\)

\(=2x^3-16x^2+32x-x^3-5x^2+4x+20+2x^2+20x+50-x^2+2x-1\)

\(=x^3-20x^2+58x+69\)

c, Ta có :\(\left(x+5\right)^2-4x\left(2x+3\right)^2-\left(2x-1\right)\left(x-3\right)\left(x+3\right)\)

\(=\left(x+5\right)^2-4x\left(4x^2+12x+9\right)-\left(2x-1\right)\left(x^2-9\right)\)

\(=\left(x+5\right)^2-\left(16x^3+48x^2+36x\right)-\left(2x^3-x^2-18x+9\right)\)

\(=x^2+10x+25-16x^3-48x^2-36x-2x^3+x^2+18x-9\)

\(=-18x^3-46x^2-8x+16\)

d

a) A = (x+3)² + (x-3)(x+3) - 2(x+2)(x - 4)

        = (x + 3)(x + 3) + (x - 3)(x + 3) - 2[x(x - 4) + 2(x - 4)]

        = x(x + 3) + 3(x + 3) + x(x + 3) - 3(x + 3) - 2[x² - 4x + 2x - 8]

        = x² + 3x + 3x + 9 + x² + 3x - 3x - 9 - 2(x² - 2x - 8)

        = x² + 3x + 3x + 9 +x² + 3x - 3x - 9 - 2x² + 4x + 16

        = (x² + x² - 2x²) + (3x + 3x + 3x - 3x + 4x) + (9 - 9 + 16) = 10x + 16

Thay x = -1/2 vào biểu thức trên ta có : \(10\cdot\left(-\frac{1}{2}\right)+16=-5+16=11\)

b) \(B=\left(3x+4\right)^2-\left(x-4\right)\left(x+4\right)-10x\)

\(B=9x^2+24x+16-x\left(x+4\right)+4\left(x+4\right)-10x\)

\(B=9x^2+24x+16-x^2-4x+4x+16-10x\)

\(B=\left(9x^2-x^2\right)+\left(24x-4x+4x-10x\right)+\left(16+16\right)\)

\(B=8x^2+14x+32\)

Thay x = -1/10 vào biểu thức trên ta có : \(B=8\cdot\left(-\frac{1}{10}\right)^2+14\cdot\left(-\frac{1}{10}\right)+32=\frac{767}{25}\)

c) \(C=\left(x+1\right)^2-\left(2x-1\right)^2+3\left(x-2\right)\left(x+2\right)\)

\(C=x^2+2x+1-\left(2x-1\right)\left(2x-1\right)+3\left(x^2-4\right)\)

\(C=x^2+2x+1-2x\left(2x-1\right)+1\left(2x-1\right)+3x^2-12\)

\(C=x^2+2x+1-4x^2+2x+2x-1+3x^2-12\)

\(C=\left(x^2-4x^2+3x^2\right)+\left(2x+2x+2x\right)+\left(1-1-12\right)\)

\(C=6x-12\)

Thay x = 1 vào biểu thức ta có : C = 6.1 - 12 = 6 -12 = -6

Còn bài kia làm nốt đi

Bạn đăng từng bài 1 và tách bài ra cho dễ nhìn hơn nhé! 

3A:

a: =15x^4-5x^2-24x^4+18x^2-6x-6x^4+2x^3

=-15x^4+2x^3+13x^2-6x

b: =1/2(x^3-2/5x^2+2x)-3/4x^3-1/4x^2-x^2-x

=1/2x^3-1/5x^2+x-3/4x^3-5/4x^2-x

=-1/4x^3-29/20x^2

c: =3/2x^2(x^2-2x)-2x(x^3+x^2+1)+2(x-1)

=3/2x^4-3x^3-2x^4-2x^3-2x+2x-2

=-1/2x^4-5x^3-2

d: =x^4-2x^3+5x^3-10x^2+5/2x-x^4+x^3-x^2

=4x^3-11x^2+5/2x

 bài 1 .

a. 3 x(5x2 – 2x -1) = 15x3 – 6x2 – 3x

b. (x2+2xy -3)(-xy) = – x3y – 2x2y2 + 3xy

c. 1/2 x2y ( 2x3 – 2/5 xy2 -1 )= x5y – 1/5 x3y3 – 1/2 x2y

bài 2 . 

a) 2x^3-3x-5x^3-x^2+x^2=-3x-3x^3

b) 3x^2-6x-5x+5x^2-8x^2+24=-11x+24

c) 3x^3-3/2x^2-x^3-x/2+x/2+2=2x^3-3/2x^2+2

bài 3 .

?????????? bài 3 thì tui ko biết

Bài 3 : 

\(P=5x\left(x^2-3\right)+x^2\left(7-5x\right)-7x^2\)

\(=5x^3-15x+7x^2-5x^3-7x^2=-15x\)

Thay x = -5 vào biểu thức trên ta được 

\(-15.\left(-5\right)=75\)

Vậy x = -5 thì P = 75

thế là đủ bài rồi nhé bạn

\(a,=5x-10+2x+6=7x-4\\ b,=x^2+2x+1-x^2+3x+10=5x+11\\ c,=x^2-49-x^2+1=-48\\ d,\text{Đề có sai ko vậy?}\)

a) 2x( x - 7 ) - ( x + 3 )( x - 2 ) - ( x + 4 )( x - 4 )

= 2x² - 14x - ( x² + x - 6 ) - ( x² - 16 )

= 2x² - 14x - x² - x + 6 - x² + 16

= 22 - 15x

b) ( 2x + 5 )( x - 2 ) - 3( x + 2 )² + ( x + 1 )²

= 2x² + x - 10 - 3( x² + 4x + 4 ) + x² + 2x + 1

= 3x² + 3x - 9 - 3x² - 12x - 12

= -9x - 21

c) ( x + 3 )( x - 3 ) - ( x + 5 )( x - 1 ) - ( x - 4 )²

= x² - 9 - ( x² + 4x - 5 ) - ( x² - 8x + 16 )

= x² - 9 - x² - 4x + 5 - x² + 8x - 16

= -x² + 4x - 20

d) 2x( x + 1 )² - ( x - 1 )³ - ( x - 2 )( x² + 2x + 4 ) 

= 2x( x² + 2x + 1 ) - ( x³ - 3x² + 3x - 1 ) - ( x³ - 8 )

= 2x³ + 4x² + 2x - x³ + 3x² - 3x + 1 - x³ + 8

= 7x² - x + 9

e) ( x + 5 )( x - 5 )( x + 2 ) - ( x + 2 )³

= ( x² - 25 )( x + 2 ) - ( x³ + 6x² + 12x + 8 )

= x³ + 2x² - 25x - 50 - x³ - 6x² - 12x - 8

= -4x² - 37x - 58