I=∫010[x+110x]dx
Find I, then 9I
ϕ(x)=x+110x
ϕ(0)=0,ϕ(10)=11100≈3.01
∴[ϕ(x)]∈{0,1,2,3}
ϕ(x)=k⇔x+110x=k2
⇒x=10−k2k2
k=1: x=91,k=2: x=64=32
k=3: x=19=9,k=4: x=−616<0 (invalid)
[0,91):0;[91,32):1
[32,9):2;[9,10]:3
I=0⋅91+1⋅(32−91)+2⋅(9−32)+3⋅1
=95+350+3=9182
9I=9⋅9182=182
Answer: 182