This problem is not difficult, but the data is complex and difficult to calculate. Do you know that in parabola Y = AX 2+BX+C, the parabola axis of symmetry =-b/2a? It's good to know,

∵y=-3/5x^2+3x+ 1

Parabolic symmetry axis =-[3÷(-3/5×2)]

=3×5/6

=5/2 (2.5)

When x=5/2, y= 19/4m.

Note: It is too much trouble to solve this problem by matching method. It is best to find the value of x when y is maximum by finding the parabola symmetry axis. It's OK to bring X in! !

The second question: When x=4, just y=3.4, then the performance can be successful.

Sorry, I'm doing the problem, too. I only wrote the general process of your question. ..