Đáp án+Giải thích các bước giải:
`A=-3x^2+5x-6`
`=-3(x^2-5/3x)-6`
`=-3(x^2-5/3x+25/36-25/36)-6`
`=-3(x-5/6)^2+25/12-6`
`=-3(x-5/6)^2-47/12<=-47/12`
Dấu "=" xảy ra khi `x=5/6.`
`C=4-3x+x^2`
`=x^2-3x+9/4+7/4`
`=(x-3/2)^2+7/4>=7/4`
Dấu "=" xảy ra khi `x=3/2.`
`D=2+x^2`
Vì `x^2>=0AAx`
`=>x^2>=2AAx`
Hay `D>=2`.
Dấu "=" xảy ra khi `x=0.`
`E=x^2-5x-6`
`=x^2-5x+25/4-49/4`
`=(x-5/2)^2-49/4>=-49/4`
Dấu "=" xảy ra khi `x=5/2.`
`G=-3x^2-5x`
`=-3(x^2+5/3x)`
`=-3(x^2+5/3x+25/36-25/36)`
`=-3(x+5/6)^2+25/12<=25/12`
Dấu "=" xảy ra khi `x=-5/6.`
`H=4x^2-5x-6`
`=(2x)^2-2*2x*5/4+25/16-121/16`
`=(2x-5/4)^2-121/16>=-121/16`
Dấu "=" xảy ra khi `x=5/8.`
`I=-5x^2-4x-6`
`=-5(x^2+4/5x)-6`
`=-5(x^2+4/5x+4/25-4/25)-6`
`=-5(x+2/5)^2+4/5-6`
`=-5(x+2/5)^2-26/5<=-26/5`
Dấu "=" xảy ra khi `x=-2/5.`
`K=3-2x-x^2`
`=-(x^2+2x)+3`
`=-(x^2+2x+1-1)+3`
`=-(x+1)^2+4<=4`
Dấu "=" xảy ra khi `x=-1.`
