Ответ:

(3+x)²+(5-2x)(5+2x)-3(5-x²)=1

9+6x+x^2+25-4x^2-15+3x^2=1

19+6x=1

6x=-18

x=-3

(3+х)²+(5-2х)(5+2х)-3(5-х²)=1

9+6х+х²+25-4х²-15+3х²=1

19+6х+х²-4х²-15+2х²=1

19+6х=1

6х=1-19

6х=-18

х=-3