(1)x《10,时y=8x,
11《x《50,时y=(20-0.1(x-10)-12)x,
x》51时,y=4x
180符合第二个式子,得x=30
(2)化简y=(20-0.1(x-10)-12)x得y=-0.1x方+9,当x=45时取最大值,则20-0.1(45-10)=16.5,即最低16.5
(1)x《10,时y=8x,
11《x《50,时y=(20-0.1(x-10)-12)x,
x》51时,y=4x
180符合第二个式子,得x=30
(2)化简y=(20-0.1(x-10)-12)x得y=-0.1x方+9,当x=45时取最大值,则20-0.1(45-10)=16.5,即最低16.5