(3 - 5x)(9 + 15x + 25x^2) и найдите его значение при x = 2/5

=27+46x+75x^2-45x-75x^2-125x^2=27-125x^2

27-125(2/5)^2=27-125(4/25)= 27-20=7

(3-5х)(9+15х+25х^2)

27+45х+75х^2-45-75х-125х^2=-18-30х-5х^2

Д=900+4*5*18=1260

Х12=30+-√1260/2*(-5)