\(x+567+x-67=x+90\\ \Rightarrow\left(x+x\right)+\left(567-67\right)=x+90\\ \Rightarrow2x+500-x-90=0\\ \Rightarrow x+410=0\\ \Rightarrow x=-410\)

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

\(\Rightarrow\left\{{}\begin{matrix}x-2\sqrt{x-1}\ge0\\x-1\ge0\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\ge2\sqrt{x-1}\\x\ge1\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x^2\ge4\left(x-1\right)^2\\x\ge1\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x^2-4x^2+8x-4\ge0\\x\ge1\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}\dfrac{2}{3}\le x\le2\\x\ge1\end{matrix}\right.\\ \Rightarrow\dfrac{2}{3}\le x\le2\)

\(\left(\dfrac{4}{3}+x\right)^2=\dfrac{1}{2}\\ \Leftrightarrow\left[{}\begin{matrix}\dfrac{4}{3}+x=\dfrac{\sqrt{2}}{2}\\\dfrac{4}{3}+x=\dfrac{-\sqrt{2}}{2}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\sqrt{2}}{2}-\dfrac{4}{3}\\x=\dfrac{-\sqrt{2}}{2}-\dfrac{4}{3}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{3\sqrt{2}-8}{6}\\x=-\dfrac{3\sqrt{2}+8}{6}\end{matrix}\right.\)

\(a,cos^4a-sin^4a=2cos^2a-1\\ VT=\left(cos^2a-sin^2a\right)\left(cos^2a+sin^2a\right)\\ =cos^2a-sin^2a\\ =cos2a=2cos^2a-1\)

\(b,VT=\dfrac{cos^2a+\dfrac{sin^2a}{cos^2a}-1}{sin^2a}\\ =\dfrac{\dfrac{cos^4a+sin^2a-cos^2a}{cos^2a}}{sin^2a}\\ =\dfrac{\dfrac{cos^4a+\left(1-cos^2a\right)-cos^2a}{cos^2a}}{sin^2a}\\ =\dfrac{\dfrac{cos^4a+1-2cos^2a}{cos^2a}}{sin^2a}\\ =\dfrac{\dfrac{\left(1-cos^2a\right)^2}{cos^2a}}{sin^2a}\\ =\dfrac{sin^4a}{cos^2a}:sin^2a\\ =\dfrac{sin^4a}{cos^2a}\times\dfrac{1}{sin^2a}\\ =\dfrac{sin^2a}{cos^2a}=tan^2a\)

\(\dfrac{\left(x+3\right)}{7}+\dfrac{\left(x+4\right)}{6}+\dfrac{\left(x+90\right)}{10}+3=0\\ \Leftrightarrow\dfrac{60\left(x+3\right)}{420}+\dfrac{70\left(x+4\right)}{420}+\dfrac{42\left(x+90\right)}{420}+\dfrac{1260}{420}=0\\ \Leftrightarrow60x+180+70x+280+42x+3780+1260=0\\ \Leftrightarrow172x=-5500\\ \Leftrightarrow x=-\dfrac{1375}{43}\)

\(a,=\dfrac{\sqrt{2}.\sqrt{5}-\sqrt{3}.\sqrt{5}}{2\sqrt{2}-2\sqrt{3}}\\ =\dfrac{\sqrt{5}.\left(\sqrt{2}-\sqrt{3}\right)}{2\left(\sqrt{2}-\sqrt{3}\right)}\\ =\dfrac{\sqrt{5}}{2}\)

\(b,=\dfrac{\sqrt{3}.\sqrt{5}-\sqrt{2}.\sqrt{3}}{\sqrt{5}.\sqrt{7}-\sqrt{2}.\sqrt{7}}\\ =\dfrac{\sqrt{3}\left(\sqrt{5}-\sqrt{2}\right)}{\sqrt{7}\left(\sqrt{5}-\sqrt{2}\right)}\\ =\dfrac{\sqrt{3}}{\sqrt{7}}=\dfrac{\sqrt{21}}{7}\)

\(c,=\dfrac{\sqrt{5}.\sqrt{5}+\sqrt{5}}{\sqrt{2}.\sqrt{5}+\sqrt{2}}\\ =\dfrac{\sqrt{5}\left(\sqrt{5}+1\right)}{\sqrt{2}\left(\sqrt{5}+1\right)}\\ =\dfrac{\sqrt{5}}{\sqrt{2}}=\dfrac{\sqrt{10}}{2}\)

\(a,ĐK:5x+2\ge0\\ \Rightarrow x\ge-\dfrac{2}{5}\\ b,ĐK:3-2x\ge0\\ \Rightarrow-2x\ge-3\\ \Rightarrow x\le\dfrac{3}{2}\\ c,ĐK:7x-1\ge0\\ \Rightarrow x\ge\dfrac{1}{7}\)

\(d,ĐK:X-5\ge0\\ \Rightarrow X\ge5\)

\(E,ĐK:x+3>0\\ \Rightarrow x>-3\)

\(F,ĐK:1-2x>0\\ \Rightarrow-2x>-1\\ \Rightarrow x< \dfrac{1}{2}\)

\(G,\left\{{}\begin{matrix}x\ge0\\x+3>0\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\ge0\\x>-3\end{matrix}\right.\Rightarrow x\ge0\)

\(h,ĐK:\dfrac{-5}{2x+3}\ge0\)

Vì \(-5< 0\)

\(\Rightarrow2x+3< 0\\ \Rightarrow x< -\dfrac{3}{2}\)

\(K,ĐK:x^2-3x\ge0\)

\(\Rightarrow\left[{}\begin{matrix}x\le0\\x\ge3\end{matrix}\right.\)

\(I,ĐK:x^2+7\ge0\left(voli\right)\)

Vì \(x^2\ge0\forall x\\ 7>0\forall x\)

\(\Rightarrow x^2+7>0\)

=> vô nghiệm 

\(a,\dfrac{1}{3}-\left(-1\dfrac{2}{5}\right)+\left(-3\dfrac{1}{4}\right)\\ =\dfrac{1}{3}-\left(-\dfrac{7}{5}\right)-\dfrac{13}{4}\\ =\dfrac{1}{3}+\dfrac{7}{5}-\dfrac{13}{4}\\ =\dfrac{20}{3\times20}+\dfrac{7\times12}{5\times12}-\dfrac{13\times15}{4\times15}\\ =\dfrac{20+84-195}{60}\\ =\dfrac{-91}{60}\)

\(b,\dfrac{5}{4}-\left(-3\dfrac{1}{2}\right)-\dfrac{7}{10}\\ =\dfrac{5}{4}+\dfrac{7}{2}-\dfrac{7}{10}\\ =\dfrac{5\times5}{4\times5}+\dfrac{7\times10}{2\times10}-\dfrac{7\times2}{10\times2}\\ =\dfrac{25+70-14}{20}\\ =\dfrac{81}{20}\)

\(c,\dfrac{3}{2}-\left[\left(-\dfrac{4}{7}-\left(\dfrac{1}{2}+\dfrac{5}{8}\right)\right)\right]\\ =\dfrac{3}{2}-\left[-\dfrac{4}{7}-\left(\dfrac{4}{8}+\dfrac{5}{8}\right)\right]\\ =\dfrac{3}{2}-\left(-\dfrac{4}{7}-\dfrac{9}{8}\right)\\ =\dfrac{3}{2}+\dfrac{4}{7}+\dfrac{9}{8}\\ =\dfrac{3\times28}{2\times28}+\dfrac{4\times8}{8\times7}+\dfrac{9\times7}{8\times7}\\ =\dfrac{84+32+63}{56}\\ =\dfrac{179}{56}\)