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Ta có : x3 + 2x2 + 2x + 1
= x3 + x2 + (x2 + 2x + 1)
= x2(x + 1) + (x + 1)2
= (x + 1) ( x2 + x + 1)
a)\(\left(ab-1\right)^2+\left(a+b\right)^2=a^2b^2-2ab+1+a^2+2ab+b^2\)
\(=a^2b^2+a^2+b^2+1\)
\(=a^2\left(b^2+1\right)+\left(b^2+1\right)\)
\(\left(a^2+1\right)\left(b^2+1\right)\)
b)\(x^3+2x^2+2x+1=x^3+x^2+x^2+x+x+1\)
\(=x^2\left(x+1\right)+x\left(x+1\right)+x+1\)
\(=\left(x^2+x+1\right)\left(x+1\right)\)
= (x^4 + 2x^3 + x^2) + x + 1
= (x^2 + x)^2 + (x + 1)
= [x. (x + 1)]^2 + (x + 1)
= x^2 . (x + 1)^2 + (x + 1)
= (x + 1).[x^2. (x + 1) + 1]
= (x + 1). (x^3 + x^2 + 1)
Không hiểu hỏi lại nha :)
Dùng phương pháp nhẩm nghiệm:
x^4+2x^3+x^2+x+1=(x^4+x^3)+(x^3+x^2)+(x+1)=(x+1)(x^3+x^2+1)
x4 -2x2 +1 =x2.x2 - x2-x2 +1= - x2(1- x2) + (1 - x2)=(1-x2).(1-x2)=(1-x2)2
Bài 1:
a)\(5x^2y^3-25x^3y^4+10x^3y^3=5x^2y^3\left(1-5xy+2x\right)\)
b)\(x^3-2xy-x^2y+2y^2=\left(x^3-x^2y\right)-\left(2xy-2y^2\right)=x^2\left(x-y\right)-2y\left(x-y\right)=\left(x-y\right)\left(x^2-2y\right)\)
c)Đề sai hoàn toàn
d) \(2x^2+4xy+2y^2-8z^2=2\left(x^2+2xy+y^2-4z^2\right)=2\left[\left(x+y\right)^2-\left(2z\right)^2\right]=2\left(x+y-2z\right)\left(x+y+2z\right)\)e) \(3x-3a+yx-ya=3\left(x-a\right)+y\left(x-a\right)=\left(x-a\right)\left(3+y\right)\)
f)\(\left(x^2+y^2\right)^2-4x^2y^2=\left(x-y\right)^2\left(x+y\right)^2\)
g)\(2x^2-5x+2=2x^2-x-4x+2=x\left(2x-1\right)-2\left(2x-1\right)=\left(2x-1\right)\left(x-2\right)\)
i)\(14x\left(x-y\right)-21y\left(y-x\right)+28z\left(x-y\right)=14x\left(x-y\right)+21y\left(x-y\right)+28z\left(x-y\right)=7\left(x-y\right)\left(2x+3y+4z\right)\)