№1.а) (5 -a)²= 5² - 2*5*a + a² = a² - 10a + 25б) (4x +1)² = (4x)² + 2*4x*1 + 1² = 16x² + 8x + 1в) (3a - 7)(3a +7) = (3a)² - 7² = 9a² - 49№2.а) (a-8)(a-7)-(a-9)² = a² -7a -8a +56 - (a² - 2*a*9 + 9²) == a² - 15a + 56 - a² + 18a - 81 == (a² -a²) +(18a - 15a) - (81 - 56) = = 3a - 25б) 4b(b+1) - (2b - 1)² = 4b² + 4b - ( (2b)² - 2*2b*1 + 1² ) == 4b² + 4b - 4b² + 4b - 1 = (4b² - 4b²) + (4b + 4b) - 1 == 8b - 1в)x(x-5) + (3x+1)² = x² - 5x + (3x)² +2*3x*1 + 1² = = x² - 5x +9x² + 6x + 1= (x² + 9x²) + (6x - 5x) + 1==10x² +x + 1г) (2x-5)² -2(7x-1)² = (4x² - 20x + 25) - 2(49x² - 14x + 1) == 4x² - 20x + 25 - 98x² + 28x - 2 == -94x² + 8x + 23