Question

а) (x+5)*(x-3)+(x-5)*(x+5)=
б) (3a+7)^2-42=

Answer 1

(x+5)*(x-3) + (x-5)*(x+5) = x² - 3x + 5x - 15 + x² - 25 = 2x²+2x - 40 = 2x(x+1)-40(3a+7)² - 42 = 9a² + 42a + 49 - 42 = 9a² + 42a + 7 = a(9a+420) + 7