给滑块一初速度v₀，使它沿与水平方向夹角为30度的光滑斜面向上做匀减速运动，当滑块速度大小减为 $\frac{v_0}{2}$ 时，所用时间可能是（   ）

    Do you know how to study in a right way?The following are the ways of studying．

    First，the best time for reading is morning，because in the morning，the air is fresh and the mind is clear．For that reason，we can get good result．

    Second，in studying we must have patience．If we have not known a text well，we must read it again．We should not read the next one until we have learned the first one．

    Third，when we are studying，we must put our hearts into the book，or we can get nothing from the book while we are reading．

    At last，we must always ask“whys”．If we don't understand something well，write it down and ask our teachers or our parents for help．In any possible way,we must know it completely and what we've learned can be used well and made better.

    Though there are many ways for studying，yet the above mentioned will be quite enough if we can keep them in heart and do so．

（1）若xⁿ=2，yⁿ=3，求（x²y）²ⁿ的值．

（2）若3^a=6，9^b=2，求3^2a﹣4b+1的值．​