①y甲=25×10+(x-10)×5=5x+200;
②y乙=(25×10+5x)×0.9=4.5x+225;
③5x+200>4.5x+225,
x>50;
5x+200=4.5x+225,
x=50;
5x+200<4.5x+225,
x<50;
答:当练习本超过50本时,选择乙方案;当练习本为50本时,两种方案价钱一样;当练习本少于50本时,选择甲方案.
①y甲=25×10+(x-10)×5=5x+200;
②y乙=(25×10+5x)×0.9=4.5x+225;
③5x+200>4.5x+225,
x>50;
5x+200=4.5x+225,
x=50;
5x+200<4.5x+225,
x<50;
答:当练习本超过50本时,选择乙方案;当练习本为50本时,两种方案价钱一样;当练习本少于50本时,选择甲方案.