Đáp án:
`a)x^2-5=x^2-(sqrt5)^2=(x-sqrt5)(x+sqrt5)` $\\$ `b)x^2+2sqrt3x+3=x^2+2sqrt3x+sqrt3^2=(x+sqrt3)^2` $\\$ `c)x^2-2xsqrt{11}+11=x^2-2xsqrt{11}+sqrt{11}^2=(x-sqrt{11})^2` $\\$ `d)x-5sqrtx+6=x-2sqrtx-3sqrtx+6` $\\$ `=sqrtx(sqrtx-2)-3(sqrtx-2)=(sqrtx-2)(sqrtx-3)`