Phân tích đa thức thành nhân tử: a(b+c)2(b-c)+b(c+a)2(c-a)+c(a+b)2(a-b)
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phân tích đa thức thành nhân tử
a^2(b-c)+b^2(c-a)+c^2(a-b)
= -(b-a)(c-a)(c-b)
nha bạn
a2(b-c)+b2(c-a)+c2(a-b)
=a2b-a2c+b2c-b2a+c2(a-b)
=(a2b-b2a)-(a2c-b2c)+c2(a-b)
=ab(a-b)+c(a2-b2)+c2(a-b)
=ab(a-b)+c(a-b)(a+b)+c2(a-b)
=(a-b)(ab+ac+bc+c2)
=(a-b)[(ab+bc)+(ac+c2)]
=(a-b)[b(a+c)+c(a+c)]
=(a-b)(a+c)(b+c)
\(=a^2b-a^2c+b^2c-b^2a+c^2a-c^2b\)
\(=\left(a^2b-b^2a\right)-\left(a^2c-b^2c\right)+c^2\left(a-b\right)\)
\(=ab\left(a-b\right)-c\left(a-b\right)\left(a+b\right)+c^2\left(a-b\right)\)
\(=\left(a-b\right)\left(ab-ca-cb+c^2\right)\)
\(=\left(a-b\right)\left[a\left(b-c\right)-c\left(b-c\right)\right]\)
\(=\left(a-b\right)\left(b-c\right)\left(a-c\right)\)
\(a\left(b^2-c^2\right)-b\left(a^2-c^2\right)+c\left(a^2-b^2\right)\)
\(=ab^2-ac^2-ba^2+bc^2+ca^2-cb^2\)
\(=\left(ab^2-ac^2-bc^2\right)-\left(ba^2-bc^2-ca^2\right)\)
\(=a\left(b^2-c^2\right)-bc^2-a^2\left(b-c\right)+bc^2\)
\(=a\left(b^2-c^2\right)-a^2\left(b-c\right)\)
\(=a\left(b-c\right)\left(b+c\right)-a^2\left(b-c\right)\)
\(=\left(b+c\right)\left[a\left(b-c\right)-a^2\right]\)
\(=\left(b+c\right)\left(ab-ac-a^2\right)\)
\(a\left(b^2-c^2\right)-b\left(a^2-c^2\right)+c\left(a^2-b^2\right)\)
\(=c\left(a^2-b^2\right)+a\left(b^2-c^2\right)+b\left(c^2-a^2\right)\)
\(=-c\left[\left(b^2-c^2\right)+\left(c^2-a^2\right)\right]+a\left(b^2-c^2\right)+b\left(c^2-a^2\right)\)
\(=\left(a-c\right)\left(b^2-c^2\right)+\left(b-c\right)\left(c^2-a^2\right)\)
\(=\left(a-c\right)\left(b-c\right)\left(b+c\right)+\left(b-c\right)\left(c-a\right)\left(c+a\right)\)
\(=\left(a-c\right)\left(b-c\right)\left(b-a\right)\)
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).