Question

Giải các phương trình sau:

a.   \(x^2-5=0;\)                      b. \(x^2-2\sqrt{11}x+11=0.\)

Answer 1

a, \(x^2-5=0\Leftrightarrow\left(x-\sqrt{5}\right)\left(x+\sqrt{5}\right)=0\Leftrightarrow x=\pm\sqrt{5}\)

b, \(x^2-2\sqrt{11}+11=0\Leftrightarrow\left(x-\sqrt{11}\right)^2=0\Leftrightarrow x=\sqrt{11}\)

Answer 2

a) \(x^2-5=0\)

\(x^2=5\Leftrightarrow x=-\sqrt{5}\) hoặc \(x=\sqrt{5}\)

Vậy S={\(-\sqrt{5}\);\(\sqrt{5}\)}

b) \(x^2-2.\sqrt{11}x+11=0\)

\(x^2-2.x.\sqrt{11}+\left(\sqrt{11}\right)^2=0\)

\(\left(x-\sqrt{11}\right)^2=0\)

\(x-\sqrt{11}=0\)

\(x=\sqrt{11}\)

Vậy S={\(\sqrt{11}\)}

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