Đáp án+Giải thích các bước giải:
`a)2x^2-2sqrt2x+1`
`=(sqrt2x)^2-2sqrt2x+1`
`=(sqrt2x-1)^2`
`x-5sqrtx+6`
`=x-2sqrtx-3sqrtx+6`
`=sqrtx(sqrtx-2)-3(sqrtx-2)`
`=(sqrtx-2)(sqrtx-3)`
`b)x-sqrtx-6`
`=x-3sqrtx+2sqrtx-6`
`=sqrtx(sqrtx-3)+2(sqrtx-3)`
`=(sqrtx-3)(sqrtx+2)`
`2x+2sqrt6x+3`
`=(sqrt2x)^2+2sqrt{2}x.sqrt3+sqrt3^2`
`=(sqrt2x+sqrt3)^2`
`-5-2x^2+sqrt3x`
`=-2(x^2-sqrt3/2x)-5`
`=-2(x^2-2*x*sqrt3/4+3/16-3/16)-5`
`=-2(x-sqrt3/4)^2+3/8-5`
`=-2(x-sqrt3/4)^2-37/8<=-37/8`
Dấu "=" xảy ra khi `x=sqrt3/4`