Question

(5x-3)(5x+3)-25x²-35 x=40

Answer 1

раскррем скобки
25x^2+15x-15x-9-25x^2-35=40
приведем подобные
-9-35=40
-44=40
x=84

Answer 2

$(5x-3)(5x+3)-25 x^{2} -35x=40\\25 x^{2} -9-25 x^{2} -35x=40\\-35x=40+9\\-35x=49\\x=- \frac{49}{35} \\ \\x=- \frac{7}{5} \\ \\x=- \frac{14}{10} \\x=-1.4$