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(a-b)(b-c)(a-c)+(a+b)(c+a)(c-b)+(b+c)(c+a)(b-a)
= ( b - c) [ a2−ab−ac+bc−ac−bc−a2−ab]+(b+c)(c+a)(b−a)a2−ab−ac+bc−ac−bc−a2−ab]+(b+c)(c+a)(b−a)
= -2a.(b + c) (b - c) + (b+c)(c+a)(b-a)
= ( b + c ) ( bc + ab - ac - a2a2 - 2ab + 2ac )
= ( b + c ) ( bc - ab + ac - a2a2 )
= ( b + c ) ( a + b ) ( c - a )
\(\left(a-b\right)\left(b-c\right)\left(a-c\right)+\left(a+b\right)\left(b+c\right)\left(a-c\right)+\left(c+a\right)\left(a+b\right)\left(b-c\right)\)
\(=\left(a-c\right)\left[\left(a-b\right)\left(b-c\right)+\left(a+b\right)\left(b+c\right)\right]+\left(c+a\right)\left(a+b\right)\left(b-c\right)\)
\(=\left(a-c\right)\left(2ab+2bc\right)+\left(c+a\right)\left(a+b\right)\left(b-c\right)\)
\(=2b\left(a-c\right)\left(a+c\right)+\left(c+a\right)\left(a+b\right)\left(b-c\right)\)
\(=\left(a+c\right)\left[2b\left(a-c\right)+\left(a+b\right)\left(b-c\right)\right]\)
Ta có: \(\left(a-b\right)\left(b-c\right)\left(a-c\right)+\left(a+b\right)\left(b+c\right)\left(a-c\right)+\left(a+b\right)\left(a+c\right)\left(c-b\right)\)
\(=\left(a-c\right).\left[\left(a-b\right)\left(b-c\right)+\left(a+b\right)\left(b+c\right)\right]+\left(a+b\right)\left(a+c\right)\left(c-b\right)\)
\(=\left(a-c\right).\left(ab-ac-b^2+bc+ab+ac+b^2+bc\right)+\left(a+b\right)\left(a+c\right)\left(c-b\right)\)
\(=\left(a-c\right).\left(2ab+2bc\right)+\left(a+b\right)\left(a+c\right)\left(c-b\right)\)
\(=2b.\left(a-c\right).\left(a+c\right)+\left(a+b\right)\left(a+c\right)\left(c-b\right)\)
\(=\left(a+c\right)\left[2b\left(a-c\right)+\left(a+b\right)\left(c-b\right)\right]\)
\(=\left(a+c\right)\left(2ab-2bc+ac-ab+bc-b^2\right)\)
\(=\left(a+c\right)\left(ab-bc+ac-b^2\right)\)
\(=\left(a+c\right)\left[a.\left(b+c\right)-b.\left(b+c\right)\right]\)
\(=\left(a+c\right)\left(a-b\right)\left(b+c\right)\)
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)
\(A=\left(a+b\right)\left(b+c\right)\left(c+a\right)+abc\)
\(=a^2b+ab^2+a^2c+ac^2+b^2c+bc^2+2abc+abc\)
\(=ab\left(a+b+c\right)+bc\left(a+b+c\right)+ca\left(a+b+c\right)\)
\(=\left(a+b+c\right)\left(ab+bc+ca\right)\)
Vậy....
\(a^4\left(b-c\right)+b^4\left(c-a\right)+c^4\left(a-b\right)\)
\(\Leftrightarrow\text{=a^4(b-c)-b^4[(b-c)+(a-b)]+c^4(a-b) =(b-c)(a^4-b^4)+(a-b)(c^4-b^4)}\)
\(\text{=(b-c)(a^2-b^2)(a^2+b^2)+(a-b)(c^2-b^2)... =(b-c)(a-b)(a+b)(a^2+b^2)-(a-b)(b-c)(b+... }\)
\(\text{=(b-c)(a-b)(a^3+ab^2+ba^2+b^3-bc^2-b^3-... mà ta có a^3+ab^2+ba^2-bc^2-c^3-cb^2 }\)
\(\text{=(a^3-c^3)+b^2(a-c)+b(a^2-c^2) =(a-c)(a^2+ac+c^2)+b^2(a-c)+b(a-c)(a+c) }\)
\(\text{=(a-c)(a^2+ac+c^2+b^2+ab+ac) } \)
\(\text{từ đó suy ra a^4(b-c)+b^4(c-a)+c^4(a-b) =(a-b)(b-c)(c-a)(a^2+b^2+c^2+ab+bc+ca)}\)
=a3(b-c)-b3(a-c)+c3(a-c-b+c)
=a3(b-c)-b3(a-c)+c3(a-c)-c3(b-c)
=(a3-c3)(b-c)-(b3-c3)(a-c)
=(a-c)(a2+ac+c2)(b-c)-(b-c)(b2+bc+c2)(a-c)
=(b-c)(a-c)(a2+ac+c2-b2-bc-c2)
=(b-c)(a-c)[(a-b)(a+b)+c(a-b)]
=(a-b)(b-c)(a-c)(a+b+c)
Ta có:\(a^3\left(b-c\right)+b^3\left(c-a\right)+c^3\left(a-b\right)\)
\(=a^3\left(b-c\right)-b^3\left(a-c\right)+c^3\left(a-c-b+c\right)\)
\(=a^3\left(b-c\right)-b^3\left(a-c\right)+c^3\left(a-c\right)-c^3\left(b-c\right)\)
\(=\left(a^3-c^3\right)\left(b-c\right)-\left(b^3-c^3\right)\left(a-c\right)\)
\(=\left(a-c\right)\left(a^2+ac+c^2\right)\left(b-c\right)-\left(b-c\right)\left(b^2+bc+c^2\right)\left(a-c\right)\)
\(=\left(b-c\right)\left(a-c\right)\left(a^2+ac+c^2-b^2-bc-c^2\right)\)
\(=\left(b-c\right)\left(a-c\right)\left[\left(a-b\right)\left(a+b\right)+c\left(a-b\right)\right]\)
\(=\left(a-b\right)\left(b-c\right)\left(a-c\right)\left(a+b+c\right)\)
sai rồi phải thành phép nhân chứ