Question

数学必修五后面的思考与讨论哪里有答案?

Answer 1

2x+y=1.5(x+y)-0.5(-x+y)

∵ 1≤x+y≤2

∴ 1.5≤1.5(x+y)≤3

∵ -1≤-x+y≤1

∴ -0.5≤-0.5(-x+y)≤0.5

∴ 1≤2x+y=1.5(x+y)-0.5(-x+y)≤3.5

因此1≤f(2,1)≤3.5