5 sinx +12cosx-10
=13(5/13sinx+12/13cosx)-10
=13*sin(x+alpha)-10
-1<=sin(x+alpha)<=1
=>-13<=13sin(x+alpha)<=13
=>-23<=13sin(x+alpha)-10<=3
=>0<=y<=23
y=0 khi sin (x+alpha)=0
=>x+alpha=kpi
=>x=kpi-alpha
y=23 khi 13sin(x+alpha)-10=-23
=>sin(x+alpha)=-1
=>x+alpha=-pi/2+k2pi
=>x=-pi/2-alpha+k2pi
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