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\(\left(a-b\right)^3-\left(b-a\right)^2+b\left(a-b\right)^2\)
\(=\left(a-b\right)^3-\left(a-b\right)^2+b\left(a-b\right)^2\)
\(=\left(a-b\right)^2.\left(a-b-1+b\right)\)
\(=\left(a-b\right)^2.\left(a-1\right)\)
\(\left(a-b\right)^3-\left(b-a\right)^2+b\left(a-b\right)^2=\left(a-b\right)^3-\left(a-b\right)^2+b\left(a-b\right)^2\)
=\(\left(a-b\right)^2\left(a-b-1+b\right)=\left(a-b\right)^2\left(a-1\right)\)
\(=a^2\left(1-b^2\right)+b\left(b-1\right)+a\left(b-1\right)..\)
\(=a^2\left(1-b\right)\left(1+b\right)-b\left(1-b\right)-a\left(1-b\right).\)
\(=\left(a^2+a^2b-b-a\right)\left(1-b\right)\)
\(=\left(ab+a+b\right)\left(a-1\right)\left(1-b\right)\)
\(a^2+b^2-a^2b^2+ab-a-b\)
\(=a^2\left(1-b^2\right)+b\left(b-1\right)+a\left(b-1\right)\)
\(=a^2\left(1-b\right)\left(1+b\right)-b\left(1-b\right)-a\left(1-b\right)\)
\(=\left(a^2+a^2b-b-a\right)\left(1-b\right)\)
\(=\left(ab+a+b\right)\left(a-1\right)\left(1-b\right)\)
\(a\left(b-c\right)^2+b\left(c-a\right)^2+c\left(a-b\right)^2+8abc\)
\(=a\left(b^2-2bc+c^2\right)+b\left(c^2-2ac+a^2\right)+c\left(a^2-2ab+b^2\right)+8abc\)
\(=ab^2-2abc+ac^2+bc^2-2abc+ba^2+ca^2-2abc+cb^2+8abc\)
\(=ab^2+ac^2+bc^2+ba^2+ca^2+cb^2+2abc\)
\(=\left(ac^2+bc^2\right)+\left(ab^2+ba^2\right)+\left(ca^2+cb^2+2abc\right)\)
\(=c^2\left(a+b\right)+ab\left(a+b\right)+c\left(a^2+b^2+2ab\right)\)
\(=c^2\left(a+b\right)+ab\left(a+b\right)+c\left(a+b\right)^2\)
\(=\left(a+b\right)\left[c^2+ab+c\left(a+b\right)\right]=\left(a+b\right)\left(c^2+ab+ca+bc\right)\)
\(=\left(a+b\right)\left[\left(c^2+ca\right)+\left(ab+bc\right)\right]=\left(a+b\right)\left[c\left(c+a\right)+b\left(a+c\right)\right]\)
\(=\left(a+b\right)\left(b+c\right)\left(c+a\right)\)
a(b+c)2(b-c)+b(c+a)2(c-a)+c(a+b)2(a-b)
=(-a)c3-abc2+ab2c+ab3+bc3+abc2+(-a2)bc+(-a3)b+(-b3)c-ab2c+a2bc+a3c
=(b-a)c3+(a3-b3)c+ab3+(-a3)b
=(b-a)(c-a)(c-b)(c+b+a)
cách khác dễ hiểu hơn chỉ cần thay a,b,c =x,y,z
(x-y)3+(y-z)3+(z-x)3
=(x-y+y-z)[(x-y)2-(x-y)(y-z)+(y-z)2]+(z-x)3
=(x-z)[(x-y)2-(x-y)(y-z)+(y-z)2-(z-x)2]
=(x-z)[(x-y)(x-y-y+z)+(y-z+z-x)(y-z-z+x)]
=(x-z)(x-y)(x-2y+z-y+2z-x)
=3(x-z)(x-y)(z-y)
Gọi P là biểu thức phải phân tích, ta có
P = a(b + c)^2(b - c) + b(c + a)^2(c - a) - c(a + b)^2[(b - c) + (c - a)]
= a(b + c)^2(b - c) + b(c + a)^2(c - a) - c(a + b)^2(b - c) - c(a + b)^2(c - a)
= [a(b + c)^2(b - c) - c(a + b)^2(b - c)]+ [b(c + a)^2(c - a) - c(a + b)^2(c - a)]
= (b - c)[a(b + c)^2 - c(a + b)^2] + (c - a)[b(c + a)^2 - c(a + b)^2]
= (b - c)(ab^2 + ac^2 - ca^2 - cb^2) + (c - a)(bc^2 + ba^2 - ca^2 - cb^2)
= (b - c)[ac(c - a) - b^2(c - a)] + (c - a)[a^2(b - c) - bc(b - c)]
= (b - c)(c - a)(ac - b^2) + (c - a)(b - c)(a^2 - bc)
= (b - c)(c - a)(ac - b^2 + a^2 - bc)
= (b - c)(c - a)[(a^2 - b^2) + (ac - bc)]
= (b - c)(c - a)[(a - b)(a + b) + c(a - b)]
= (b - c)(c - a)(a - b)(a + b + c)
= (a - b)(b - c)(c - a)(a + b + c).
Vậy P = (a - b)(b - c)(c - a)(a + b + c).
a2(b-c)+b2(c-a)+c2(a-b)= a2b - a2c + b2c - b2a + c2a - c2b
=a2b + b2c - a2c - c2b - b2a + c2a
=b(a2 + bc) - c(a2 + bc) - a(b2 - c2)
=(a2 + bc)(b - c) - a(b - c)(b + c) =(b - c)[a2 + bc - a(b + c)]
=(b-c)(a2-ab -ac +bc)= (b-c)[a(a-b) - c(a-b)] = (b - c)(a - b)(a - c)
Ta có :
\(\left(a-b\right)^2-\left(b-a\right)\left(a+b\right)\)
\(=\)\(\left(a-b\right)^2+\left(a-b\right)\left(a+b\right)\)
\(=\)\(\left(a-b\right)\left(a-b+a+b\right)\)
\(=\)\(\left(a-b\right)2a\)
\(=\)\(2a\left(a-b\right)\)
Chúc bạn học tốt ~