Y=√(-500-60x-x²)
x²+60x+500≤0
x1+x2=-60 U x1*x2=500
x1=-50 U x2=-10
D(y)∈[-50;-10]
y`=(-60-2x)/2√(-500-60x-x²)=(-30-x)/√(-500-60x-x²)=0
-30-x=0
x=-30
+ _
--------------------(-30)-------------------
max
ymax=√(-500-60*(-30)-900)=√(-500+1800-900)=√400=20