Câu 1 Làm tính nhân
a) 2xy.(\(3x^2+2y-1\))
b) (\(x^2+3xy\))(\(x^2y-3xy^2-7\))
Câu 2 Phân tích đa thức thành nhân tử
a) \(x^3-9x\)
b)\(x^2.\left(x+3\right)+12-4x\)
c) x.(x+2)+x-2
Câu 3 Làm tính chia
\(\left(30x^3y^4+45x^2y^3-10x^2y^2\right):5x^2y\)
Câu 4 Tìm x
a) \(x^3-4x=0\)
b)\(\left(x+1\right)^2-\left(x+1\right)\left(x-1\right)=0\)
Làm giúp mk với
Thanks
Câu 1:
\(a,2xy\left(3x^2+2y-1\right)\)
\(=2xy.3x^2+2xy.2y-2xy.1\)
\(=6x^3y+4xy^2-2xy\)
\(b,\left(x^2+3xy\right)\left(x^2y-3xy^2-7\right)\)
\(=x^2.x^2y-x^2.3xy^2-x^2.7+3xy.x^2y-3xy.3xy^2-3xy.7\)
\(=x^4y-3x^3y^2-7x^2+3x^3y^2-9x^2y^3-21xy\)
\(=x^4y-7x^2-9x^2y^3-21xy\)
Câu 2:
\(a,x^3-9x\)
\(=x\left(x^2-9\right)\)
\(=x\left(x-3\right)\left(x+3\right)\)
\(b,x^2\left(x+3\right)+12-4x\) ( sai đề )
Sửa :
\(x^2\left(x+3\right)-12-4x\)
\(=x^2\left(x+3\right)-\left(12+4x\right)\)
\(=x^2\left(x+3\right)-4\left(x+3\right)\)
\(=\left(x+3\right)\left(x^2-4\right)\)
\(=\left(x+3\right)\left(x-2\right)\left(x+2\right)\)
\(c,x\left(x+2\right)-x-2\)
\(=x\left(x+2\right)-\left(x+2\right)\)
\(=\left(x+2\right)\left(x-1\right)\)
Câu 3:
Cách 1: \(\left(30x^3y^4+45x^2y^3-10x^2y^2\right):\left(5x^2y\right)\)
\(=5x^2y\left(6xy^3+9y^2-2y\right):5x^2y\)
\(=6xy^3+9y^2-2y\)
Cách 2: \(\left(30x^3y^4+45x^2y^3-10x^2y^2\right):\left(5x^2y\right)\)
\(=30x^3y^4:5x^2y+45x^2y^3:5x^2y-10x^2y^2:5x^2y\)
\(=6xy^3+9y^2-2y\)
Câu 4:
\(a,x^3-4x=0\)
\(\Rightarrow x\left(x^2-4\right)=0\)
\(\Rightarrow x\left(x-2\right)\left(x+2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x-2=0\\x+2=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)
\(b,\left(x+1\right)^2-\left(x+1\right)\left(x-1\right)=0\)
\(\Rightarrow\left(x+1\right)\left(x+1-x+1\right)=0\)
\(\Rightarrow2\left(x+1\right)=0\)
\(\Rightarrow x+1=0\)
\(\Rightarrow x=-1\)
