已知a＞0,函数f(x)=ax-bx2.(1)当b＞0时,若对任意x∈R都有f(x)≤1,证明;(2)当b＞1时,证明对任意x∈［0,1］,|f(x)|≤1的充要条件是b-1≤a≤;(3)当0＜b≤1时,讨论:对任
已知a,b都是实数，那么“”是“a>b”的 A. 充分而不必要条件 B. 必要而不充分条件 C. 充分必要条件
阅读下面的文字，按要求作文。 “天街小雨润如酥，草色遥看近却无”是唐代诗人韩愈的名句。诗句的意思是说，在滋润如酥的初春细雨中，春草发芽
I enjoyed the pictures of the river and they brought back the old days _____ I swam in it. A. when B. that C. who D. where
About of the students in our class _______ born in the Year of Snake. A. two-thirds; are B. two third; were C. two-thirds; were D. two-third; was
室温下，PH相同、体积相同的醋酸和盐酸分别采取下列措施，有关叙述正确的是( ) A.加入适量醋酸钠晶体后，两溶液的PH均增大 B.将温度升高至50℃，
下列计算一定正确的是 （A） ． （B） ． （C） ． （D） ．
They are fighting ______ us _______ the enemy. A. with; against B. for; against C. with; for D. with; at
对应的点在( )