\[2 \cdot (x + 6)^{2} - (20x + 70) =\]
\[= 2 \cdot \left( x^{2} + 2 \cdot 6x + 36 \right) - 20x - 70 =\]
\[= 2x^{2} + 24x + 72 - 20x - 70 =\]
\[= 2x^{2} + 4x + 2.\]