Question

giải các hệ phương trình

\(\left\{{}\begin{matrix}\dfrac{2x+1}{4}-\dfrac{y-2}{3}=\dfrac{1}{12}\\\dfrac{x+5}{2}=\dfrac{y+7}{3}-4\end{matrix}\right.\)

b2.

\(A=\sqrt{3+\sqrt{5}}+\sqrt{7-3\sqrt{5}}-\sqrt{2}\)

B3. Tìm ĐKXĐ

\(\dfrac{1}{x\sqrt{x}+1}-\dfrac{2}{\sqrt{x}+1}\)

b4. so sánh A với 1

A=\(\dfrac{\sqrt{x}}{x-\sqrt{x}+1}\)

b5.tính

a,\(\sin47+2\sin38-\cos43-\cos52\)

b, \(C=\dfrac{2\sin^2x-1}{\sin x-\cos x}\)

Answer 1

Bài 2: 

Ta có: \(A=\sqrt{3+\sqrt{5}}+\sqrt{7-3\sqrt{5}}-\sqrt{2}\)

\(=\dfrac{\sqrt{6+2\sqrt{5}}+\sqrt{14-6\sqrt{5}}-2}{\sqrt{2}}\)

\(=\dfrac{\sqrt{5}+1+3-\sqrt{5}-2}{\sqrt{2}}=\sqrt{2}\)