Question

(2c-5)^2-(2x-3)(2x+3)

Answer 1

$(2c-5)^2-(2x-3)(2x+3)=4c^2-20c+25-(2x-3)(2x+3)$$=4c^2-20c+25+(-2x+3)(2x+3)=$$=4c^2-20c+25-4x^2-6x+6x+9=4c^2-20c+34-4x^2$$=4c^2-4x^2-20c+34$

Answer 2

=2с^2-20с+25-4х^2-6х+6х+9=2с^2-20с+34-4х^2
неверно так