解 设(5/4)^x=t,
则原试等于 t+1/t≤41/20
20t^2+20≤41t
20t^2-41t+20≤0
(4t-5)(5t-4)≤0
解得t≤5/4 或t≤4/5
则(5/4)^x≤5/4 或(5/4)^x≤4/5
答案自己计算吧