\[\boxed{\text{834.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ (x - 10)^{2} - x(x + 80) =\]
\[= x^{2} - 20x + 100 - x^{2} - 80x =\]
\[= - 100x + 100\]
\[если\ x = 0,97:\]
\[( - 100) \cdot 0,97 + 100 = - 97 +\]
\[+ 100 = 3\]
\[\textbf{б)}\ (2x + 9)^{2} - x(4x + 31) =\]
\[= 4x^{2} + 36x + 81 - 4x^{2} -\]
\[- 31x = 5x + 81\]
\[если\ x = - 16,2:\]
\[\ 5 \cdot ( - 16,2) + 81 = - 81 +\]
\[+ 81 = 0\]
\[\textbf{в)}\ (2x + 0,5)^{2} - (2x - 0,5)^{2} =\]
\[= 4x^{2} + 2x + 0,25 -\]
\[- \left( 4x^{2} - 2x + 0,25 \right) =\]
\[= 4x^{2} + 2x + 0,25 - 4x^{2} +\]
\[+ 2x - 0,25 = 4x\]
\[если\ x = - 3,5:\]
\[4 \cdot ( - 3,5) = - 14\]
\[\textbf{г)}\ (0,1x - 8)^{2} + (0,1x + 8)^{2} =\]
\[= 0,01x^{2} - 1,6x + 64 +\]
\[+ 0,01x^{2} + 1,6x + 64 =\]
\[= 0,02x + 128\]
\[если\ x = - 10:\]
\[0,02 \cdot ( - 10)^{2} + 128 = 2 +\]
\[+ 128 = 130.\]