2x^2-7x+2
=2(x^2-7/2x)+2
=2(x-7/4)^2+2-49/8
=2(x-7/4)^2-33/8
所以有最小值,即X=7/4时,最小值是:-33/8
-3x^2+5x+1
= -3(x^2-5/3x)+1
=-3(x-5/6)^2+1+25/12
=-3(x-5/6)^2+37/12
所以有最大值,即当X=5/6时,最大值是:37/12
2x^2-7x+2
=2(x^2-7/2x)+2
=2(x-7/4)^2+2-49/8
=2(x-7/4)^2-33/8
所以有最小值,即X=7/4时,最小值是:-33/8
-3x^2+5x+1
= -3(x^2-5/3x)+1
=-3(x-5/6)^2+1+25/12
=-3(x-5/6)^2+37/12
所以有最大值,即当X=5/6时,最大值是:37/12