1)(x+9)²-x(x+8)=1
x²+18x+81-x²-8x-1=0
10x=-80
x=-8
2)(x-11)²=(x-7)(x-9)
x²-22x+121-x²+9x+7x-63=0
-6x=-58
x=58/6=9 2/3
3)16-(6-11x)²=0
(6-11x)²=16
6-11x=-4 U 6-11x=4
11x=6+4=10 U 11x=6-4=2
x=10/11 U x=2/11
3)(7m-13)²-(9m+19)²=0
(7m-13-9m-19)(7m-13+9m+19)=0
(-2m-32)(16m+6)=0
-2m-32=0⇒-2m=32⇒m=-16
16m+6=0⇒16m=-6⇒m=-3/8