1) a^2+4b^2-1
2) b^4+3b^3+9b^2+27b-3b^3-9b^2-27b-81=b^4-81
1089=33*33=1089
121=11*11=121
64=8*8=64
72.25=8,5*8,5=72.25
55000-х+0.1×(55000-х)=44000
55000-х+5500-0.1х=44000
-1.1х=-16500
х=15000
х-у=0
х-2=2
x-y=0
x=4
4-y=0
y=4
(x, y) = (4, 4)
4-4=0
4-2=2
0=0
2=23
(x, y) = (4, 4)
3
6
7
4^(n+1)*3^(n+1)/4^(n-2)=4^3*3*3^n=64*3*15=2880