Câu 1:
a) \(=10x^3+15x^2-5x\)
b) \(=15x^2+14x-8-2x+2=15x^2+12x-6\)
Bài 2:
a) \(=5x\left(x-9\right)\)
b) \(=x\left(x-4\right)+y\left(x-4\right)=\left(x-4\right)\left(x+y\right)\)
c) \(=\left(x+2\right)^2-y^2=\left(x+2-y\right)\left(x+2+y\right)\)
Bài 3:
a) \(\Rightarrow\left(x-3\right)\left(5x+4\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=3\\x=-\dfrac{4}{5}\end{matrix}\right.\)
b) \(\Rightarrow9-x^2+x^2-2x+1=0\Rightarrow2x=10\Rightarrow x=5\)