a: \(\left(a+1\right)^2-\left(a-1\right)^2\)
\(=\left(a+1-a+1\right)\left(a+1+a-1\right)\)
\(=4a\)
b: \(\left(x+5\right)^2-x^2\)
\(=\left(x+5-x\right)\left(x+5+x\right)\)
\(=5\left(2x+5\right)\)
1) \(\left(a+1\right)^2-\left(a-1\right)^2\)
= \(\left(a+1-a+1\right)\left(a+1+a-1\right)\)
= \(2.2a\)
=\(4a\)
2)\(\left(x+5\right)^2-x^2\)
=\(\left(x+5-x\right)\left(x+5+x\right)\)
=5.\(\left(2x+5\right)\)
3)\(\left(x+2\right)^2-9x^2\)
=\(\left(x+2\right)^2-\left(3x\right)^2\)
=\(\left(x+2-3x\right)\left(x+2+3x\right)\)
4)\(\left(3x+1\right)^2-\left(5x-1\right)^2\)
=\(\left(3x+1-5x+1\right)\left(3x+1+5x-1\right)\)
=\(\left(-2x+2\right).8x\)