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a: (3x^2-4)(x+3y)
=3x^2*x+3x^2*3y-4x-4*3y
=3x^3+9x^2y-4x-12y
b: (c+3)(x^2+3x)
=c*x^2+c*3x+3x^2+9x
=cx^2+3cx+3x^2+9x
c: (xy-1)(xy+5)
=xy*xy+5xy-xy-5
=x^2y^2+4xy-5
d: (3x+5y)(2x-7y)
=3x*2x-3x*7y+5y*2x-5y*7y
=6x^2-21xy+10xy-35y^2
=6x^2-11xy-35y^2
e: -(x-1)(-x^2+2y)
=(x-1)(x^2-2y)
=x^3-2xy-x^2+2y
f: (-x^2+2y)(x^2+2y)
=(2y)^2-x^4
=4y^2-x^4
b: \(x^2-6x+xy-6y\)
\(=x\left(x-6\right)+y\left(x-6\right)\)
\(=\left(x-6\right)\left(x+y\right)\)
c: \(2x^2+2xy-x-y\)
\(=2x\left(x+y\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(2x-1\right)\)
e: \(x^3-3x^2+3x-1=\left(x-1\right)^3\)
A=x(x + 2y) - 2x (3x - y) + 5 (x2 - xy) - (20 - xy)
=x2+2xy-6x2+2xy+5x2-5xy-20+xy
=-20
B=x2 (2x - 3) -x (2x2 + 5) + 3x2 + 5x + 20
=2x3-3x2-2x3+-5x+3x2+5x+20
Câu cuối bạn viết ko rõ
a) Xem lại đề
b) x³ - 4x²y + 4xy² - 9x
= x(x² - 4xy + 4y² - 9)
= x[(x² - 4xy + 4y² - 3²]
= x[(x - 2y)² - 3²]
= x(x - 2y - 3)(x - 2y + 3)
c) x³ - y³ + x - y
= (x³ - y³) + (x - y)
= (x - y)(x² + xy + y²) + (x - y)
= (x - y)(x² + xy + y² + 1)
d) 4x² - 4xy + 2x - y + y²
= (4x² - 4xy + y²) + (2x - y)
= (2x - y)² + (2x - y)
= (2x - y)(2x - y + 1)
e) 9x² - 3x + 2y - 4y²
= (9x² - 4y²) - (3x - 2y)
= (3x - 2y)(3x + 2y) - (3x - 2y)
= (3x - 2y)(3x + 2y - 1)
f) 3x² - 6xy + 3y² - 5x + 5y
= (3x² - 6xy + 3y²) - (5x - 5y)
= 3(x² - 2xy + y²) - 5(x - y)
= 3(x - y)² - 5(x - y)
= (x - y)[(3(x - y) - 5]
= (x - y)(3x - 3y - 5)
g. \(x^{^3}+3x^2+3x+1-27z^3\\ =\left(x^{^3}+3x^2+3x+1\right)-27z^3\\ =\left(x+1\right)^3-27z^3\\ =\left(x+1-3\right)\left[\left(x+1\right)^2+\left(x+1\right)3z+9z^2\right]\\ =\left(x-2\right)\left(x+2x+1+3zx+3z+9z^2\right)\\ =\left(x-2\right)\left(3x+3zx+3z+9z^2+1\right)\left(x-2\right)3x\left(1+z\right)+3z\left(1+z\right)+1\\ =\left(x-2\right)\left(1+z\right)\left(3x+3z\right)+1\\ =\left(x-2\right)\left(1-z\right)3\left(x+z\right)+1\)
Mk lm hơi tắt, bn chú ý nha:
a,\(x^3\left(x+1\right)+\left(x+1\right)=\left(x+1\right)\left(x^3+1\right)\)
=\(\left(x+1\right)\left(x+1\right)\left(x^2-x+1\right)\)
=\(\left(x+1\right)^2\left(x^2-x+1\right)\)
b,\(\left(x^4-x^3\right)-\left(x^2-1\right)\)
=\(x^3\left(x-1\right)-\left(x-1\right)\left(x+1\right)\)
= \(\left(x-1\right)\left(x^3-x-1\right)\)
c,Đề phải thế này nha:
\(x^2y-xy^2-x+y\)=\(xy\left(x-y\right)-\left(x-y\right)\)
=\(\left(x-y\right)\left(xy-1\right)\)
d,hình như đề sai đó bn, thế này đúng ko?
\(a^2x+a^2y-7x-7y\)=\(a^2\left(x+y\right)-7\left(x+y\right)\)=\(\left(x+y\right)\left(a^2-7\right)\)
e,\(4x^2-x^2-16y^2+4y^2\)
=\((4x^2-16y^2)-\left(x^2-4y^2\right)\)
=\(4\left(x-2y\right)\left(x+2y\right)-\left(x^2-2y\right)\left(x^2+2y\right)\)=\(3\left(x-2y\right)\left(x+2y\right)\)
Cách này nhanh hơn:\(3\left(x^2-4y^2\right)\)
=\(3\left(x-2y\right)\left(x+2y\right)\)
g,\(\left(x+1\right)^3-\left(3z\right)^3\)=
\(\left(x-3z+1\right)[\left(x+1\right)^2+3z\left(x+1\right)+9z^2]\)Nếu thấy đề bn đưa sai thì nhắc mk nhé?
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