Вот ответ на 1 вопрос
1)
(x+7)²+2(x+7)(x-5)+(x-5)²=x²+14x+49+2(x²-5x+7x-35)+x²-10x+25=x²+14x+49+2x²-10x+14x-70+x²-10x+25=4x²+8x+4=(2x+2)²
при x=3.5
(2*3.5+2)²=9²=81
2)
(10x-5)²-(8x-3)²+4x=100x²-100x+25-(64x²-48x+9)+4x=100x²-100x+25-64x²+48x-9+4x=36x²-48x+16=(6x-4)²
при x=3
(6*3-4)²=14²=196
Вот ответ на 1 вопрос
1)
(x+7)²+2(x+7)(x-5)+(x-5)²=x²+14x+49+2(x²-5x+7x-35)+x²-10x+25=x²+14x+49+2x²-10x+14x-70+x²-10x+25=4x²+8x+4=(2x+2)²
при x=3.5
(2*3.5+2)²=9²=81
2)
(10x-5)²-(8x-3)²+4x=100x²-100x+25-(64x²-48x+9)+4x=100x²-100x+25-64x²+48x-9+4x=36x²-48x+16=(6x-4)²
при x=3
(6*3-4)²=14²=196