题目

已知函数f(x)＝log4(4x＋1)＋2kx(k∈R)是偶函数． (1)求k的值； (2)若方程f(x)＝m有解，求m的取值范围． 答案： 解析:(1)由函数f(x)是偶函数可知，f(－x)＝f(x)，∴log4(4x＋1)＋2kx＝log4(4－x＋1)－2kx，即log4＝－4kx，∴log44x＝－4kx，∴x＝－4kx，即(1＋4k)x＝0，对一切x∈R恒成立，∴k＝－.……6分 (2)由m＝f(x)＝log4(4x＋1)－x＝log4＝log4(2x＋),∵2x>0,∴2x＋≥2,∴m≥log42＝. 故要使方程f(x)＝m有解，m的取值范围为[，＋∞)．…The dam is 3800 ___. It is a 980 ___ dam at the base. metres long, metres wide B.metres-long, metres wide  C.metres long, metre-wide D. metre—long, metres wide