36n²-49=(6n+7)(7-6n)
36n²-49=(7+6n)(7-6n)
36n²-49=7²-(6n)²
36n²-49=49-36n²
72n²=98
n²=98/72
n²=49/36
n₁=7/6; n₂=-7/6
(x+y=0
(2x-y=9
3х=9
х=9:3
х=3
3+у=0
у=0-3
у=-3
7
a²-6a+9-5a²+6a=9-4a²
a=-1/2 9-4*(-1/2)²=9-4*1/4=9-1=8
9
3ac²/[(a-4c)(a+4c)*(a-4c)/ac=3c/(a+4c)
a=2,1;c=-0,4
3*(-0,4)/(2,1-1,6)=-1,2/0,5=-2,4