ĐKXĐ: \(-1\le x\le4\)

\(pt\Leftrightarrow\dfrac{x+1-4\left(4-x\right)}{\sqrt{x+1}+2\sqrt{4-x}}=\dfrac{5\left(x-3\right)}{\sqrt{2x^2+18}}\)

\(\Leftrightarrow\dfrac{5\left(x-3\right)}{\sqrt{x+1}+2\sqrt{4-x}}=\dfrac{5\left(x-3\right)}{\sqrt{2x^2+18}}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\\sqrt{x+1}+2\sqrt{4-x}=\sqrt{2x^2+18}\left(1\right)\end{matrix}\right.\)

Xét (1):

\(\Leftrightarrow x+1+4\left(4-x\right)+4\sqrt{\left(x+1\right)\left(4-x\right)}=2x^2+18\)

\(\Leftrightarrow2x^2+3x+1-4\sqrt{-x^2+3x+4}=0\)

\(\Leftrightarrow2x^2-x-3+4\left(x+1-\sqrt{-x^2+3x+4}\right)=0\)

\(\Leftrightarrow2x^2-x-3+\dfrac{4\left(2x^2-x-3\right)}{x+1+\sqrt{-x^2+3x+4}}=0\)

\(\Leftrightarrow2x^2-x-3=0\)

\(9\sqrt{x}< \frac{15}{2}\Leftrightarrow\sqrt{x}=\frac{5}{6}\Leftrightarrow x=\frac{25}{36}\)

Thay =vào biểu thức ta được :

3,5√0,7 − 1,4 + 2,5√0,7 − 2,6 / 0,7 + 3√0,7  −2,7

=

b)Thay =-√5 vào biểu thức. 

=30−30(−√5)/−10+10(−√5)=

\(a,ĐK:x\ge\dfrac{1}{5}\\ PT\Leftrightarrow5x-1=64\\ \Leftrightarrow x=13\left(tm\right)\\ b,ĐK:x\ge\dfrac{2}{5}\\ BPT\Leftrightarrow5x-2< 16\\ \Leftrightarrow x< \dfrac{18}{5}\\ \Leftrightarrow\dfrac{2}{5}\le x< \dfrac{18}{5}\\ c,ĐK:x\ge3\\ PT\Leftrightarrow\left|x-1\right|-\left|x-2\right|=x-3\\ \Leftrightarrow\left[{}\begin{matrix}1-x-\left(2-x\right)=x-3\left(x< 1\right)\\x-1-\left(2-x\right)=x-3\left(1\le x< 2\right)\\x-1-\left(x-2\right)=x-3\left(x\ge2\right)\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=2\left(ktm\right)\\x=0\left(tm\right)\\x=4\left(tm\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)

a, 4x²=15-(-21)

=36

x²=36:4

x²=4

x²=2²

x=2

b. 5x²+7,1=\(\sqrt{49}\)

\(\Rightarrow\)5x²+7,1=7

\(\Rightarrow\)5x^{2 = 7+7,1}

^{\(\Rightarrow\)}5x² =14,1

\(\Rightarrow\)x² =\(\dfrac{14,1}{5}\)

\(\Rightarrow\)x =\(\sqrt{\dfrac{14,1}{5}}\)

cho mk 1 tick đúng và câu tiếp thao sẽ hiện ra