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a) 2x² - xy + 4x - 2y
<=> (2x² + 4x)-(xy + 2y)
<=> 2x(x + 2) - y(x + 2)
<=> (x + 2)(2x - y)
b) (a²−a+2012)(a²−a+2014)−3
Đặt a²−a+2012 là x , ta có :
x(x + 2) - 3
<=> x² + 2x - 3
<=> x² + 3x - x - 3
<=> x(x + 3) - (x + 3)
<=> (x +3)(x - 1)
Thay x = a²−a+2012 , ta được :
(a²−a+2015)(a²−a+2011)
a3(c - b2) + b3(a - c2) + c3(b - a2) + abc(abc - 1)
= a3c - a3b2 + ab3 - b3c2 + bc3 - a2c3 + a2b2c2 - abc
= a2b2c2 - b3c2 - (a2c3 - bc3) - (a3b2 - ab3) + (a3c - abc)
= b2c2(a2 - b) - c3(a2 - b) - ab2(a2 - b) + ac(a2 - b)
= (a2 - b)(b2c2 - c3 - ab2 + ac) = (a2 - b)[c2(b2 - c) - a(b2 - c)] = (a2 - b)(b2 - c)(c2 - a)
`a^2 + ab + 2a + 2b = a(a+2) + b(a+2) = (a+b)(a+2)`
\(B=\left(a^2+b^2\right)^3+\left(c^2-a^2\right)^3-\left(b^2+c^2\right)^3\)
\(=\left(a^2+b^2+c^2-a^2\right)\left[\left(a^2+b^2\right)^2-\left(c^2-a^2\right)\left(a^2+b^2\right)+\left(c^2-a^2\right)^2\right]-\left(b^2+c^2\right)^2\)
\(=\left(b^2+c^2\right)\left[\left(a^2+b^2\right)^2-\left(c^2-a^2\right)\left(a^2+b^2\right)+\left(c^2-a^2\right)^2\right]-\left(b^2+c^2\right)^2\)
\(=\left(b^2+c^2\right)\left(a^4+2a^2b^2+b^4-a^2c^2+a^4-b^2c^2+a^2b^2-b^4-2b^2c^2-c^4\right)\)
\(=\left(b^2+c^2\right)\left(2a^4-c^4+3a^2b^2-a^2c^2-3b^2c^2\right)\)
ko chắc
\(\left(a+b\right)\left(a^2-b^2\right)+\left(b+c\right)\left(b^2-c^2\right)+\left(c+a\right)\left(c^2-a^2\right)\)
\(=\left(a+b\right)\left(a^2-b^2\right)-\left(b+c\right)\left[c^2-a^2+a^2-b^2\right]+\left(c+a\right)\left(c^2-a^2\right)\)
\(=\left(a+b\right)\left(a^2-b^2\right)-\left(b+c\right)\left(c^2-a^2\right)-\left(b+c\right)\left(a^2-b^2\right)+\left(c+a\right)\left(c^2-a^2\right)\)
\(=\left(a^2-b^2\right)\left(a+b-b-c\right)+\left(c^2-a^2\right)\left(c+a-b-c\right)\)
\(=\left(a-b\right)\left(a+b\right)\left(a-c\right)+\left(c-a\right)\left(c+a\right)\left(a-b\right)\)
\(=\left(a-b\right)\left(a-c\right)\left(a+b-c-a\right)\)
\(=\left(a-b\right)\left(a-c\right)\left(b-c\right)\)
Chúc bạn học tốt.
\(\left(a^2+a\right)^2+3\left(a^2+a\right)-10\)
\(=\left(a^2+a+5\right)\left(a^2+a-2\right)\)
\(=\left(a^2+a+5\right)\left(a-1\right)\left(a+2\right)\)