Question

ō.ō

求解🙏🙏🙏🙏🙏

Answer 1

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戦場ヶ原ヒタギ✖︎両儀式

y=2k*t*(4-t), t>=0.
If 4-t<=0, then y<=0, no need to discuss, so we may assume 0<t<4. (t>0, 4-t>0)
To find max{y}, we can apply the Cauchy-Schwartz inequality, [t+(4-t)]/2>=sqrt (t(4-t)), then t(4-t)<=4.
For the sake of safety, the shell should be kept away from the ceiling, so y<32. Then max{y}=2k*4<32, we make a conclusion that k with range (0, 4).