【1】配方法过程
2x^2-4x+5
2[x^2-(2/1)x]+5
2[x^2-2·x+1^2-1^2]+5
2(x-1)^2+3
当x取1时,有最小值=3
【2】配方法过程
-3x^2+6x-5
-3[x^2-(2/1)x]-5
-3[x^2-2·(1/1)x+(1/1)^2-(1/1)^2]-5
-3(x-1/1)^2-2
当x取1时,有最大值= -2