Вопрос:

Ответ:

\[(7 - x)(7 + x) + (x + 3)^{2} =\]

\[= 49 - x^{2} + x^{2} + 6x + 9 =\]

\[= 6x + 58\]

\[x = - 3,5:\]

\[6x + 58 = 6 \cdot ( - 3,5) + 58 =\]

\[= - 21 + 58 = 37.\]