(x²+8²)-x²≤11x
x²+64-x²≤11x
11x≥64/:11
x≥64/11
x²-(9-x)²>-2x
x²-(81-18x+x²)>-2x
x²-x²+81+18x+2x>0
20x>-81/:20
x<-4,05<br>
(12+x)²≥x²+21x
144+24x+x²≥x²+21x
x²-x²+24x-21x≥-144
3x≥-144/:3
x≥-48
x²<(25-x)²+25x<br>x²<625-50x+x²+25x<br>x²-x²+50x-25x<625<br>25x<625/:25<br>x<25