-2х²+5х=0
-х(2х-5)=0
х=0
2х-5=0
2х=5
х=5/2
х=2,5
Пусть x - 3 = t
t^2 + 9t + 20 = 0
D= 81 - 80 = 1
t1 = ( - 9 + 1)/2 = - 8/2 = - 4;
t2 = ( - 9 - 1)/2 = - 10/2 = - 5;
x - 3 = - 4
x = - 1
x - 3 = - 5
x = - 2
? : (х-2)=(х+3)+5
?=(х-2)*(х+3)+5
?=х²-2х+3х-6+5=х²+х-1
?=х²+х-1