Đáp án:
$\displaystyle \begin{array}{{>{\displaystyle}l}} 11.\ \left( 2+\sqrt{x}\right)^{2}\\ 12.\ \left( 2+\sqrt{x}\right)^{2}\\ 13.\ ( 2x-1)^{2}\\ 14.\ \left(\sqrt{x} -1\right)\left( x+\sqrt{x} +1\right)\\ 27.\ \left(\sqrt{x} -11\right)\left(\sqrt{x} -1\right)\\ 28.\ \left(\sqrt{x} -1\right)\left(\sqrt{x} -6\right)\\ 29.\ \left( 2\sqrt{x} -1\right)\left(\sqrt{x} -2\right)\\ 30.\ \left( -\sqrt{x} +1\right)\left(\sqrt{x} -2\right) \ \end{array}$
Giải thích các bước giải:
$\displaystyle \begin{array}{{>{\displaystyle}l}} 11.\ x-10\sqrt{x} +25=\left( 2+\sqrt{x}\right)^{2}\\ 12.\ 4+4\sqrt{x} +x=\left( 2+\sqrt{x}\right)^{2}\\ 13.\ 4x-4\sqrt{x} +1=( 2x-1)^{2}\\ 14.\ x\sqrt{x} -1=\left(\sqrt{x} -1\right)\left( x+\sqrt{x} +1\right)\\ 27.\ x-12\sqrt{x} +11=x-\sqrt{x} -11\sqrt{x} +11\\ =\sqrt{x}\left(\sqrt{x} -1\right) -11\left(\sqrt{x} -1\right)\\ =\left(\sqrt{x} -11\right)\left(\sqrt{x} -1\right)\\ 28.\ x-7\sqrt{x} +6=x-6\sqrt{x} -\sqrt{x} +6\\ =\sqrt{x}\left(\sqrt{x} -6\right) -\left(\sqrt{x} -6\right)\\ =\left(\sqrt{x} -1\right)\left(\sqrt{x} -6\right)\\ 29.\ 2x-5\sqrt{x} +2=2x-4\sqrt{x} -\sqrt{x} +2\\ =2\sqrt{x}\left(\sqrt{x} -2\right) -\left(\sqrt{x} -2\right)\\ =\left( 2\sqrt{x} -1\right)\left(\sqrt{x} -2\right)\\ 30.\ -x+3\sqrt{x} -2=-x+2\sqrt{x} +\sqrt{x} -2\\ =-\sqrt{x}\left(\sqrt{x} -2\right) +\left(\sqrt{x} -2\right)\\ =\left( -\sqrt{x} +1\right)\left(\sqrt{x} -2\right) \end{array}$
