Bài 1:
a: \(\left(x+3\right)^2=x^2+6x+9\)
b: \(\left(3x-1\right)^2=9x^2-6x+1\)
c: \(\left(x+3\right)\left(3-x\right)=9-x^2\)
d: \(\left(x-\dfrac{1}{2}\right)\left(x+\dfrac{1}{2}\right)=x^2-\dfrac{1}{4}\)
e: \(\left(2x+3y\right)^2=4x^2+12xy+9y^2\)
f: \(\left(x^2-3y\right)^2=x^4-6x^2y+9y^2\)
g: \(\left(2xy+1\right)\left(2xy-1\right)=4x^2y^2-1\)
Bài 2:
a: Ta có: \(M=\left(x+2\right)\left(x-5\right)+\left(1-x\right)^2\)
\(=x^2-5x+2x-10+x^2-2x+1\)
\(=2x^2-5x-9\)
b: Ta có: \(N=\left(x+1\right)\left(x-1\right)-x\left(2x+1\right)\)
\(=x^2-1-2x^2-x\)
\(=-x^2-x-1\)
c: Ta có: \(P=3x\left(2-5x\right)-\left(x+2\right)\left(x-2\right)\)
\(=6x-15x^2-x^2+4\)
\(=-16x^2+6x+4\)
d: Ta có: \(Q=\left(3x+2\right)\left(3x-1\right)-\left(x+3\right)^2\)
\(=9x^2-3x+6x-2-x^2-6x-9\)
\(=8x^2-3x-11\)
e: Ta có: \(P=\left(2x+3y\right)\left(2x-3y\right)-\left(2x-y\right)^2\)
\(=4x^2-9y^2-4x^2+4xy-y^2\)
\(=-10y^2+4xy\)
