Question

(2х-1)(2х+1)-(2-х)^2+(3х+1)^2=18

Answer 1

4x^2 - 1 - (4 - 4x + x^2) + 9x^2 + 6x + 1 = 18
4x^2 - 1 - 4 + 4x - x^2  + 9x^2 + 6x + 1 - 18 = 0 
4x^2 - 5 + 4x + 8x^2 + 6x - 17 = 0 
12x^2 + 10x - 22 = 0   /:2
6x^2 + 5x - 11 = 0 
D = 25 + 264 = 289 
x1 = ( - 5 + 17)/12 = 1
x2 = ( - 5  - 17)/12 = - 11/6