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a/ 9a^3 - 13a + 6 = 9a^3 - 6a^2 + 6a^2 - 4a - 9a + 6 = (9a^3 - 6a^2) + (6a^2 - 4a) - (9a - 6) = 3a^2(3a - 2) + 2a(3a - 2) - 3(3a - 2) = (3a^2 + 2a - 3)(3a - 2) Mình gửi luôn cho nóng^^Được câu nào hay câu đó. Yên tâm mình sẽ cố nghĩ &gửi nốt :)))
b/x^4 - 4x^3 + 8x + 3 = x^4 - 3x^3 - x^3 + 3x^2 - 3x^2 + 9x - x + 3 = (x^4 - 3x^3) - (x^3 - 3x^2) - (3x^2 - 9x) - (x - 3) = x^3(x - 3) - x^2(x - 3) - 3x(x - 3) - (x - 3) = (x^3 - x^2 - 3x - 1)(x - 3) Mình đang cố nghĩ nốt con c đây, có vẻ khó^^
\(a,2x^2-4x+2=2\left(x^2-2x+1\right)=2\left(x-1\right)^2\)
\(b,4x-4y+x^2\left(y-x\right)=4\left(x-y\right)-x^2\left(x-y\right)=\left(x-y\right)\left(2-x\right)\left(2+x\right)\)
\(c,2xz+y^2-x^2-z^2=y^2-\left(x^2-2xz+z^2\right)=y^2-\left(x-z\right)^2=\left(y-x+z\right)\left(y+x-z\right)\)
\(d,3a^2-3ab+9b-9a=3a\left(a-b\right)-9\left(a-b\right)=\left(3a-9\right)\left(a-b\right)=3\left(a-3\right)\left(a-b\right)\)
\(f,x^2+5x+6=x^2+2x+3x+6=x\left(x+2\right)+3\left(x+2\right)=\left(x+2\right)\left(x+3\right)\)
Bài 1: 4a2-4ab+b2-9a2b2
=(2a)2-2.2a.b+b2-(3ab)2
=(2a-b)2-(3ab)2
=(2a-b-3ab)(2a-b+3ab)
a/ (4a2-4ab+b2)-9a2b2
= (2a-b)2-(3ab)2
= (2a-b-3ab) (2a-b+3ab)
a) \(a^3-b^3-3ab\left(a-b\right)\)
\(=a^3-3a^2b+3ab^2-b^3\)
\(=\left(a-b\right)^3\)
b) \(2x^3+x^2-4x-12\)
\(=2x^3-4x^2+5x^2-10x+6x-12\)
\(=2x^2\left(x-2\right)+5x\left(x-2\right)+6\left(x-2\right)\)
\(=\left(2x^2+5x+6\right)\left(x-2\right)\)
c) \(x^3-3x^2+2\)
\(=x^3-x^2-2x^2+2x-2x+2\)
\(=x^2\left(x-1\right)-2x\left(x-1\right)-2\left(x-1\right)\)
\(=\left(x^2-2x-2\right)\left(x-1\right)\)
a) \(a^3-b^3-3ab\left(a-b\right)=\left(a-b\right)^3\)
b) \(2x^3+x^2-4x-12=2x^3-4x^2+5x^2-10x+6x-12\)
\(=2x^2\left(x-2\right)+5x\left(x-2\right)+6\left(x-2\right)\)
\(=\left(x-2\right)\left(2x^2+5x+6\right)\)
c) \(x^3-3x^2+2=x^3-x^2-2x^2+2\)
\(=x^2\left(x-1\right)-2\left(x-1\right)\left(x+1\right)\)
\(=\left(x-1\right)\left(x^2+2x+2\right)\)
1/ \(\left(a-b\right)\left(a^2+3ab+b^2\right)+\left(a+b\right)^3+ab\left(b-a\right)=\left(a^2+2ab+b^2+ab\right)\left(a-b\right)+\left(a+b\right)^3+ab\left(b-a\right)\)= \(\left(a^2+2ab+b^2\right)\left(a-b\right)+\left(a+b\right)ab+\left(a-b\right)^3-ab\left(a-b\right)\)
= \(\left(a+b\right)^2\left(a-b\right)+\left(a+b\right)^3\)
= \(\left(a+b\right)^2\left(a-b+a+b\right)=2a\left(a+b\right)^2\)
k mình nhé!
\(A=x^3+4x^2-8x-8=\left(x^3-8\right)+4x\left(x-2\right)=\left(x^3-2^3\right)+4x\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+4\right)+4x\left(x-2\right)=\left(x-2\right)\left(x^2+2x+4+4x\right)=\left(x-2\right)\left(x^2+6x+4\right)\)
\(B=a^2+b^2-a^2b^2+ab-a-b=\left(ab-a\right)-\left(a^2b^2-a^2\right)+\left(b^2-b\right)\)
\(=a\left(b-1\right)-a^2\left(b^2-1\right)+b\left(b-1\right)=a\left(b-1\right)-a^2\left(b-1\right)\left(b+1\right)+b\left(b-1\right)\)
\(=\left(b-1\right)\left(a-a^2b-a^2+b\right)\)
\(C=x^4-x^3-x+1=x^3\left(x-1\right)-\left(x-1\right)=\left(x-1\right)\left(x^3-1\right)\)
Đoàn Thị Huyền Đoan: Hình như câu A bạn chép xuống bị sai đề rồi!
a) ta có: (ab -1)^2 +(a+b)^2 =(ab)^2 -2ab +1 +a^2 +2ab +b^2 = a^2.(b^2 +1)+(b^2 +1)+(2ab-2ab)=(b^2 +1)(a^2 +1)
b)ta có: x^4 +2.x^3 -4x-4=[(x^2)^2 +2.(x^2).x +x^2 ] -(x^2 +2.2.x +4)=(x^2 +x)^2 -(x+2)^2=(x^2 +x+x+2)(x^2 +x-x-2)=(x^2 +2x+2)(x^2 -2)