a)\(\left(x+5\right)\cdot\left(x-5\right)-\left(x^2-1\right)\)
\(\Leftrightarrow x^2-25-x^2+1\)
\(\Leftrightarrow-24\)
b)\(\left(4x+1\right)^2+\left(4x-1\right)^2-2\cdot\left(4x+1\right)\cdot\left(4x-1\right)\)
\(\Leftrightarrow\left[\left(4x+1\right)+\left(4x-1\right)\right]^2\)
\(\left(4x+1+4x-1\right)^2\Leftrightarrow\left(8x\right)^2=64x^2\)