làm hộ đi mấy bạn $4)D=-3x^2+4x-5(x-2)$ tại $x=1$,$5)E=4x(2x-3)-5x(x-2)$ tại $x=2$,Bài 4: Chứng minh giá trị của các biểu thức sau không phụ thuộc vào biệ,$1)A=-3x(x-5)+3(x^2-4x)-3x+10$,$2)B=4x(x^2-7x+2)-4(x^3-7x^2+2x-5)$,$3)C=5x(x^2-x)-x^2(5x-5)-15$,$4)D=7(x^2-5x+3)-x(7x-35)-14$,$5)E=x^2-4x-x(x-4)-15$,Bài 5: Tính (rút gọn),$1)(3x+5)(2x-7)$ $2)(-5x+2)(-3x-4)$,$3)(x-5)(4x-3)$ $4)(x^2-2x-1)(x-3)$,$5)(x-5)(-x^2+x-1)^0$ $6)(2x-1)(x^2-5x+3)$,$7)(-x+4)(-x^2+4x-1)$ $8)(\frac12x+3)(2x^2-4x-6)$,$9)(\frac32x-1)(-4x^2+2x-6)$ $10)(-^2_3x+3)(3x^2-6x+9)$,$11)4x^2-(x+3)(x-5)+x$ $12)5x-3+(x-5)(x+4)-7$,$13)x^2-2x+5-(x-7)(x+2)$ $14)-3x+7x-9+(x-1)(x+2)$,$15)x(x-5)-3x(x+1)$ $16)4x(x^2-x+1)-(x-1)(x^2-x)$,$17)-5x(x-5)+(x-3)(x^2-7)$ $18)x(x^2-5x+2)-(x+3)(x^2-2)$,$19)4x(x^2-x-1)-(x^2-2)(x+3)$ $20)(x-5)(x+7)-7x(x+3)$,$21)x(x^2-x-2)-(x+5)(x-1)$ $22)(x+5)(x-7)-(x-4)(x+3)$,$23)(x-1)(x+2)-(x+5)(x-2)$ $24)(2x-3)(x+4)+(-x+1)(x-2$,$25)(-x+5)(x+3)+(2x-1)(x+3)$,$26)(x+3)(x-1)-(x-7)(x-6)$,$27)(-x-2)(x+1)-(x-5)(-x+1)$,$28)5x(x-3)(x-1)-4x(x^2-2x)$,$29)-4x(x+3)(x-4)-3x(x^2-x+1)$,$30)-3(x+4)(x-7)+7(x-5)(x-1)$,$31)4x(x^2-x+3)-(x-6)(x-5)$,Bài 6: Tìm x, biết,$1)4x(x-5)-(x-1)(4x-3)=5$ $\begin{array}l2)(3x-4)(x-2)=3x(x-9)-3\4)5x(x-3)-1\end{array}$,$3)(x-5)(x-4)-(x+1)(x-2)=7$ $\begin{array}l4)5x(x-3)=(x-2)(5x-1)-5\end{array}$,$5)(x-5)(x-1)=(x-1)(x-2)$ $6)6(x-3)(x-4)-6x(x-2)=4$,$7)-(x+3)(x-4)+(x-1)(x+1)=10$,$8)(2x-1)(x-2)-(x+3)(2x-7)=3$,$9)(x-5)(-x+4)-(x-1)(x+3)=-2x^2$

Question

Accepted Answer

$\displaystyle \begin{array}{{>{\displaystyle}l}}
Bài\ 4:\
1.\
A=-3x( x-5) +3\left( x^{2} -4x ight) -3x+10\
A=-3x^{2} +15x+3x^{2} -12x-3x+10\
A=10\
2.\
B=4x\left( x^{2} -7x+2 ight) -4\left( x^{3} -7x^{2} +2x-5 ight)\
B=4x^{3} -28x^{2} +8x-4x^{3} +28x^{2} -8x+20\
B=20\
3.\
C=5x\left( x^{2} -x ight) -x^{2}( 5x-5) -15\
C=5x^{3} -5x^{2} -5x^{3} +5x^{2} -15\
C=-15\
4.\
D=7\left( x^{2} -5x+3 ight) -x( 7x-35) -14\
D=7x^{2} -35x+21-7x^{2} +35x-14\
D=21-14=7\
5.\
E=x^{2} -4x-x( x-4) -15\
E=x^{2} -4x-x^{2} +4x-15\
E=-15
\end{array}$