若1>x>0,则x(3-3x)取最大值时x的值是

x(3-3x)
=3x-3x^2
顶点在-b/2a
=-(3/-6)
=1/2
x=1/2

-3x^2+3x=-3(x^2-x+1/4)+3/4=-3(x-1/2)^2+3/4
所以最大值为3/4

y=x(3-3x)=-3x²+3x
-3[x²-x+(1/2)²-(1/2)²]+3/4=y
y=-3(x-1/2)²+3/4
∴当x=1/2是
y最大=3/4
看不来问我