-2x^2+3x-1=-2（x²-3/2x)-1=-2(x²-3/2x+9/16)+9/8-1=-2(x-3/4)²+1/8≤1/8二次三项式-2x^2+3x-1的最大值是1/8
解:-2x^2+3x-1=-2(x^2-3/2x+(3/4)^2-(3/4)^2) -1=-2(x-3/4)^2 +3/8-1所以最大值为3/8-1=-5/8
