1/Phân tích đa thức thành nhân tử:
1/5x2-10xy+5y2-20z2
2/-x- y2+ x2-y
3/x(x+y)-5x-5y
4/16x-5x2-3
5/x2-5x+5y-y2
6/3x2-6xy+3y2-12z2
7/x2-y2+2yz-z2
8/2x2+7x+5
9/x2-z2+y2-2xy
10/x2-2xy-4z2+y2
11/x2+4x+3
12/5x3-5x2y-10x2+10xy
13/x3-3x2+1-3x
14/x2-6xy-25z2+9y2
15/x2-y2-x-y
16/x2-y2+4-4x
17/a3-ay-a2x+xy
18/x6-y6
19/2x2+3x-5
20/(a2+1)2-4a2
đăng nhiều thế, từng câu 1 thôi bạn
câu 20
\(\)\(C_{20}=\left(a^2+1\right)^2-4a^2=\left(a^2+1\right)^2-\left(2a\right)^2=\left[\left(a^2+1\right)-2a\right]\left[\left(a^2+1\right)+2a\right]\)\(C_{20}=\left[a^2-2a+1\right]\left[a^2+2a+1\right]=\left(a-1\right)\left(a-1\right)\left(a+1\right)\left(a+1\right)\)
\(C_{20}=\left(a-1\right)\left(a-1\right)\left(a+1\right)\left(a+1\right)\)
câu 1\(5x^2-10xy+5y^2-20z^2=5\left(x^2-2xy+y^2-4z^2\right)=5\left[\left(x^2-2xy+y^2\right)-\left(2z\right)^2\right]=5\left[\left(x-y\right)^2-\left(2z\right)^2\right]=5\left(x-y-2z\right)\left(x-y+2z\right)\)
