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a, = (xy-y^2) + (2x-2y) = y(x-y) + 2.(x-y) = (x-y).(y+2)
b, = (x+y)^2 - 9 = (x+y-3).(x+y+3)
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1)P\(=9\left(x+3\right)^2-4\left(x-2\right)^2\)\(=\left(3x+9\right)^2-\left(2x-4\right)^2\)
\(=\left(3x+9+2x-4\right)\left(3x+9-2x+4\right)\)(hằng đẳng thức số 3)
\(=\left(5x+5\right)\left(x+13\right)\)
\(=5\left(x+1\right)\left(x+13\right)\)
2)P\(=25\left(2x-y\right)^2-16\left(x+2y\right)^2\)\(=\left(10x-5y\right)^2-\left(4x+8y\right)^2\)
\(=\left(14x+3y\right)\left(6x-13y\right)\)(tương tự câu 1)
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phan tich cac da thuc sau thanh nhan tu theo mau:
a)\(2x^3-x\)
\(=x\left(2x^2-1\right)\)
\(=x\left(\left(\sqrt{2}x\right)^2-1^2\right)\)\
\(=x\left(\sqrt{2}x-1\right)\left(\sqrt{2}x+1\right)\)
b)\(5x^2\left(x-1\right)-15x\left(x-1\right)\)
\(=\left(5x^2-15x\right)\left(x-1\right)\)
\(=5x\left(x-3\right)\left(x-1\right)\)
d)\(3x\left(x-2y\right)+6y\left(2y-x\right)\)
\(=3x\left(x-2y\right)-6y\left(x-2y\right)\)
\(=\left(3x-6y\right)\left(x-2y\right)\)
\(=3\left(x-2y\right)\left(x-2y\right)\)
\(=3\left(x-2y\right)^2\)
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Lưu ý rằng ba điều kiện đầu tiên yếu tố như (x + 1) ^ 2, do đó chúng ta có:
x^2 + 2x + 1 - y^2 = (x + 1)^2 - y^2.
(x + 1)^2 - y^2 = [(x + 1) + y][(x + 1) - y], từ a^2 - b^2 = (a + b)(a - b)
= (x + y + 1)(x - y + 1).
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Đặt \(A=\left(x-y+4\right)^2-\left(3x+3y-1\right)^2\)
Ta có:
\(\left(x-y+4\right)^2=x^2-xy+4x-yx+y^2-4y+4x-4y+16\)
\(=x^2+y^2-2xy+8x-8y+16\)
\(\left(3x+3y-1\right)^2=9x^2+9xy-3x+9xy+9y^2-3y-3x-3y+1\)
\(=9x^2+9y^2-6x-6y+18xy+1\)
Mình làm đến đây bạn trừ 2 kết quả cho nhau rồi sẽ ra
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4x4 - 21 x2y2 + y4
= (4x4 + 4x2y2 + y4) - 25x2y2
= [(2x2)2 + 2x2 . 2 . y2 + (y2)2] - 25x2y2
= (2x2 + y2) - 25x2y2
= (2x2 + y2 - 5xy) (2x2 + y2 + 5xy)
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\(\left(1+2x\right).\left(1-2x\right)-x.\left(x+2\right).\left(x-2\right)\))
\(=1-\left(2x\right)^2-x.x^2-2^2\)
\(=1-4x^2-x^3-4\)
Ko bt có đúng ko nữa