(5х+3)^2-(5х-1)(5х+1)=28х+4
25х^2+30х+9-(25х^2-1)=28х+4
25х^2+30х+9-25х^2+1=28х+4
30х-28х=4-9-1
2х=-6
х=-3
ответ: -3
(5х+3)^2-(5х-1)(5х+1)=28х+4
25х^2+30х+9-(25х^2-1)=28х+4
25х^2+30х+9-25х^2+1=28х+4
30х-28х=4-9-1
2х=-6
х=-3
ответ: -3