\[(7 - x)(7 + x) + (x + 3)^{2} =\]
\[= 49 - x^{2} + x^{2} + 6x + 9 =\]
\[= 6x + 58\]
\[x = - 3,5:\]
\[6x + 58 = 6 \cdot ( - 3,5) + 58 =\]
\[= - 21 + 58 = 37.\]