Bài 1:
a) (2x - y) + (2x - y) + (2x - y) + 3y
= 3(2x - y) + 3y
= 3(2x - y + 3y)
= 3(2x + 2y)
= 3.2(x + y)
= 6(x + y)

b) (x + 2y) + (x - 2y) + (8x - 3y)
= x + 2y + x - 2y + 8x - 3y
= 9x - 3y
= 3(3x - y)

c) (x + 2y) - 2(x - 2y) - (2x - 3y)
= x + 2y - 2x + 4y - 2x + 3y
= 9y - 3x
= 3(3y - x)

Bài 2:
M + 2(x² - 4y²) + Q = 6x² - 4xy + 5y² + P
M + 2x² - 8y²   -3x² + 7xy - 2y² = 6x² - 4xy + 5y² + 9x² - 6xy + 3y²
M + 2x² - 3x² - 6x² - 9x² - 8y² - 2y² - 5y² - 3y² + 7xy + 4xy + 6xy = 0
M - 16x² - 18y² + 17xy = 0
M = 16x² + 18y² - 17xy

Biến đổi mỗi đa thức theo hướng làm xuất hiện thừa số x+y-2 \(M=x^3+x^2y-2x^2-xy-y^2+3y+x-1\)

\(M=x^3+x^2y-2x^2-xy-y^2+\left(2y+y\right)+x-\left(-2+1\right)\)

\(M=\left(x^3+x^2y-2x^2\right)-\left(xy+y^2-2y\right)+\left(x+y-2\right)+1\)

\(M=\left(x^2.x+x^2.y-2x^2\right)-\left(x.y+y.y-2y\right)+\left(x+y-2\right)+1\)

\(M=x^2.\left(x+y-2\right)-y.\left(x+y-2\right)+\left(x+y-2\right)+1\)

\(M=x^2.0+y.0+0+1\)

\(M=1\)

\(N=x^3+x^2y-2x^2-xy^2+x^2y+2xy+2y+2x-2\)

\(N=x^3+x^2y-2x^2-xy^2+x^2y+2xy+2y+2x-\left(-4+2\right)\)

\(N=\left(x^3+x^2y-2x^2\right)-\left(x^2y+xy^2-2xy\right)+\left(2x+2y-4\right)+2\)

\(N=\left(x^2x+x^2y-2x^2\right)-\left(xyx+xyy-2xy\right)+\left(2x+2y-4\right)+2\)

\(N=x^2\left(x+y-2\right)-xy\left(x+y-2\right)+2\left(x+y-2\right)+2\)

\(N=x^2.0-xy.0+2.0+2\)

\(N=2\)

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

\(P=\left(x^4+x^3y-2x^3\right)+\left(x^3y+x^2y^2-2x^2y\right)-\left(x^2+xy-2x\right)+3\)\(P=\left(x^3x+x^3y-2x^3\right)+\left(x^2y.x+x^2yy-2x^2y\right)-\left(xx+xy-2x\right)+3\)

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

\(P=x^3.0+x^2y.0-x.0+3\)

\(P=3\)

Tích mình nha!

Mà bài này hình như học ở lớp 7 rồi!

A - B = (x³y - 2xy + 5xy² - 3x²y² - 1) - (-2x³y - xy² + 2x²y² - xy + 8)

        = x³y - 2xy + 5xy² - 3x²y² - 1 + 2x³y + xy² - 2x²y² + xy - 8

        = (x³y + 2x³y) + (-2xy + xy) + (5xy² + xy²) + (-3x²y² - 2x²y²) + (-1 - 8)

        = 3x³y  - xy + 6xy² - 5x²y² - 9

a-b=(x^3y-2xy+5xy^2-3x^2y^2-1)-(-2x^3y-xy^2+2x^2y^2-xy+8)

        =x^3y-2xy+5xy^2-3x^2y^2-1+2x^3y+xy^2-2x^2y^2+xy-8

       =x^3y+(-2xy+xy)+(5xy^2+xy^2)+(-3x^2y^2-2x^2y^2)+(-1-8)

       =x^3y-1xy+6xy^2-5x^2y^2-9

\(A-B=(x^3y-2xy+5xy^2-3x^2y^2-1)-(-2x^3y-xy^2+2x^2y^2-xy+8)\)

\(=(x^3y+2x^3y)+(-2xy+xy)+(5xy^2+xy^2)+(-3x^2y^2-2x^2y^2)+(-1-8)\)

\(=3x^3y-xy+4xy^2-5x^2y^2-9\)

Chúc bạn học tốt

2) Ta có:

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

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

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

Do \(x+y-2=0\Rightarrow x+y=2\)

\(\Rightarrow B=\left(x^4+x^3y-2x^3\right)+\left(x^3y+x^2y^2-2x^2y\right)-\left[2x-2x\right]+3\)

\(=x^3.\left(x+y-2\right)+x^2y\left(x+y-2\right)-0+3\)

\(=0+0+3\)

\(=3\)

Vậy \(B=3\)

1) Ta có:

\(A=x^3+x^2y-2x^2-xy-y^2+3y+x-1\)

\(=\left(x^3+x^2y-2x^2\right)-\left(xy+y^2-2y\right)+y+x-1\)

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

\(=0+0+0+1\)

\(=1\)

Vậy \(A=1\)

a) P = \(x^2+3x+y^2-3y-2xy+90\)

= \(\left(x-y\right)^2+3\left(x-y\right)+90\)

= \(5^2+3.5+90=130\)

b) P = \(4x^2+9y^2-12xy-12x+24xy-18y+118\)

= \(4x^2+9y^2+12xy-12x-18y+118\)

= \(\left(2x+3y\right)^2-6\left(2x+3y\right)+118\)

= \(\left(-7\right)^2-6.\left(-7\right)+118=209\)

Các bạn ơi cho tui hỏi câu này : noise in / kept / night / the / awake / city / at / the / him / .

Giúp mình với , cảm ơn.

a) \(P=x\left(x+3\right)+y\left(y-3\right)-2xy+90\\ P=x^2+3x+y^2-3y-2xy+90\\ P=\left(x^2+y^2-2xy\right)+\left(3x-3y\right)+90\\ P=\left(x-y\right)^2+3\left(x-y\right)+90\\ P=5^2+3.5+90\\ P=130\)

b) \(P=\left(2x-3y\right)^2-12x\left(1-2y\right)-18y+118\\ P=4x^2-12xy+9y^2-12x+24xy-18y+118\\ P=\left(4x^2+12xy+9y^2\right)-6\left(2x+3y\right)+118\\ P=\left(2x+3y\right)^2-6\left(2x+3y\right)+118\\ P=\left(-7\right)^2-6.\left(-7\right)+118\\ P=49+42+118=209\)

1. G= 3x²y - 2xy² + x³y³ + 3xy² - 2x²y - 2x³y³

G = x²y + xy² - x³y³ = xy (x + y -x²y²)  . Khi x= -2 . y=4 ta có G= -2*4( -2 + 4 - (-2)² * 4² ) = 496

a. B+A =( -2x² + xy +2y² -5x +2y - 3) + ( x² -3xy -y² +2x -3y +1)= -x² - 2xy + y² -3x -y -2 

A-B= -( -2x² +xy + 2y² -5x +2y -3) + ( x² -3xy -y² + 2x -3y +1) = 3x² -4xy -3y² +7x -5y +4

Tại x = -1, y =2

A= (-1)² -3*(-1)*2 -2² +2*(-1) -3*2 +1 = -4

B= -2*(-1)² + (-1)*2 + 2*2² -5*(-1) + 2*2 -3 = 10

Câu 2 bạn xem lại đề nhé. hình như bạn nhầm đề!