Đáp án + giải thích các bước giải:
a) `x^2-7=x^2-(\sqrt{7})^2=(x-\sqrt{7})(x+\sqrt{7}) `
b) `x^2-3=x^2-(\sqrt{3})^2=(x-\sqrt{3})(x+\sqrt{3})`
c) `x^2-11=x^2-(\sqrt{11})^2=(x-\sqrt{11})(x+\sqrt{11})`
d) `x-3=(\sqrt{x})^2-(\sqrt{3})^2=(\sqrt{x}-\sqrt{3})(\sqrt{x}+\sqrt{3})`
e) `x-9=(\sqrt{x})^2-3^2=(\sqrt{x}-3)(\sqrt{x}+3)`
f) `x-4=(\sqrt{x})^2-2^2=(\sqrt{x}-2)(\sqrt{x}+2)`
g) `x^2-2\sqrt{7}x+7=x^2-2.x.\sqrt{7}+(\sqrt{7})^2=(x-\sqrt{7})^2`
h) `x^2+4\sqrt{3}x+12=x^2+2.x.2\sqrt{3}+(2\sqrt{3})^2=(x+2\sqrt{3})^2`
i) `x^2-2\sqrt{23}x+23=x^2-2.x.\sqrt{23}+(\sqrt{23})^2=(x-\sqrt{23})^2`
