Bài 4:
a: \(\sqrt{6^2+8^2}-3\sqrt{25}\)
\(=\sqrt{36+64}-3\cdot5\)
\(=\sqrt{100}-15=10-15=-5\)
b: \(\left(-5\dfrac{1}{2}\right)\left(-\dfrac{1}{2}\right)-\sqrt{\dfrac{4}{3^2}}\cdot\left(-\dfrac{2}{3}\right)\)
\(=\left(-\dfrac{11}{2}\right)\left(-\dfrac{1}{2}\right)-\dfrac{2}{3}\cdot\left(-\dfrac{2}{3}\right)\)
\(=\dfrac{11}{4}+\dfrac{4}{9}=\dfrac{99+16}{36}=\dfrac{115}{36}\)
c: \(\sqrt{16}\cdot\sqrt{4}-\sqrt{25}+2\sqrt{49}\)
\(=4\cdot2-5+2\cdot7\)
\(=8-5+14=22-5=17\)
d: \(\dfrac{1}{\sqrt{36}}+\dfrac{\sqrt{25}}{6}-\sqrt{0,81}\)
\(=\dfrac{1}{6}+\dfrac{5}{6}-0,9\)
=1-0,9
=0,1
e: \(-\dfrac{\sqrt{9}}{16}+\dfrac{5}{\sqrt{36}}\)
\(=-\dfrac{3}{16}+\dfrac{5}{6}\)
\(=\dfrac{-9+40}{48}=\dfrac{31}{48}\)
f: \(\dfrac{\sqrt{9}}{8}\cdot\dfrac{16}{\sqrt{225}}-\dfrac{3}{4\sqrt{4}}\cdot\dfrac{2}{5\sqrt{3^2}}\)
\(=\dfrac{3}{8}\cdot\dfrac{16}{15}-\dfrac{3}{4\cdot2}\cdot\dfrac{2}{5\cdot3}\)
\(=\dfrac{3}{15}\cdot\dfrac{16}{8}-\dfrac{1}{20}\)
\(=\dfrac{1}{5}\cdot2-\dfrac{1}{20}=\dfrac{2}{5}-\dfrac{1}{20}=\dfrac{7}{20}\)
Bài 4:
a) \(\sqrt{6^2+8^2}-3\sqrt{25}\)
\(=\sqrt{36+64}-3\cdot5\)
\(=\sqrt{100}-15\)
\(=10-15\)
\(=-5\)
b) \(\left(-5\dfrac{1}{2}\right)\cdot\left(-\dfrac{1}{2}\right)-\sqrt{\dfrac{4}{3^2}}\cdot\left(-\dfrac{2}{3}\right)\)
\(=\left(-\dfrac{11}{2}\right)\cdot\left(-\dfrac{1}{2}\right)-\dfrac{\sqrt{4}}{\sqrt{3^2}}\cdot\left(-\dfrac{2}{3}\right)\)
\(=\dfrac{11}{4}-\dfrac{2}{3}\cdot\left(-\dfrac{2}{3}\right)\)
\(=\dfrac{11}{4}+\dfrac{4}{9}\)
\(=\dfrac{115}{36}\)
c) \(\sqrt{16}\cdot\sqrt{4}-\sqrt{25}+2\sqrt{49}\)
\(=4\cdot2-5+2\cdot7\)
\(=8-5+14\)
\(=17\)
d) \(\dfrac{1}{\sqrt{36}}+\dfrac{\sqrt{25}}{6}-\sqrt{0,81}\)
\(=\dfrac{1}{6}+\dfrac{5}{6}-0,9\)
\(=1-0,9\)
\(=0,1\)
e) \(-\dfrac{\sqrt{9}}{16}+\dfrac{5}{\sqrt{36}}\)
\(=-\dfrac{3}{16}+\dfrac{5}{6}\)
\(=\dfrac{31}{48}\)
f) \(\dfrac{\sqrt{9}}{8}\cdot\dfrac{16}{\sqrt{225}}-\dfrac{3}{4\sqrt{4}}\cdot\dfrac{2}{5\cdot\sqrt{3^2}}\)
\(=\dfrac{3}{8}\cdot\dfrac{16}{15}-\dfrac{3}{4\cdot2}\cdot\dfrac{2}{5\cdot3}\)
\(=\dfrac{3\cdot16}{8\cdot15}-\dfrac{3\cdot2}{4\cdot2\cdot5\cdot3}\)
\(=\dfrac{2}{5}-\dfrac{1}{20}\)
\(=\dfrac{7}{20}\)
a) \(2,4-3x\cdot0,5=0,9\)
\(\Rightarrow3x\cdot0,5=2,4-0,9\)
\(\Rightarrow3x\cdot0,5=0,5\)
\(\Rightarrow3x=1\)
\(\Rightarrow x=\dfrac{1}{3}\)
b) \(\left|8,8x-50\right|:0,4=51\)
\(\Rightarrow\left|8,8x-50\right|=20,4\)
TH1: \(8,8x-50=20,4\Rightarrow8,8x=70,4\Rightarrow x=8\)
TH2: \(8,8x-50=-20,4\Rightarrow8,8x=29,6\Rightarrow x=\dfrac{37}{11}\)
c) \(\left|\dfrac{3}{4}x-\dfrac{3}{4}\right|=\left|-\dfrac{3}{4}\right|\)
\(\Rightarrow\dfrac{3}{4}\left|x-1\right|=\dfrac{3}{4}\)
\(\Rightarrow\left|x-1\right|=1\)
TH1: \(x-1=1\Rightarrow x=2\)
TH2: \(x-1=-1\Rightarrow x=0\)
d) \(\left(3x-4\right)^2=\left(-\dfrac{3}{4}\right)^2\)
TH1: \(3x-4=-\dfrac{3}{4}\)
\(\Rightarrow3x=\dfrac{13}{4}\Rightarrow x=\dfrac{13}{12}\)
TH2: \(3x-4=\dfrac{3}{4}\)
\(\Rightarrow3x=\dfrac{19}{4}\Rightarrow x=\dfrac{19}{12}\)
e) \(\left(\dfrac{1}{3}\right)^{2x-1}=3^5\)
\(\Rightarrow\left(\dfrac{1}{3}\right)^{2x-1}=\left[\left(\dfrac{1}{3}\right)^{-1}\right]^5\)
\(\Rightarrow\left(\dfrac{1}{3}\right)^{2x-1}=\left(\dfrac{1}{3}\right)^{-5}\)
\(\Rightarrow2x-1=-5\)
\(\Rightarrow2x=-4\)
\(\Rightarrow x=-2\)
f) \(\left|5-3x\right|+\dfrac{2}{3}=\dfrac{1}{6}\)
\(\Rightarrow\left|5-3x\right|=-\dfrac{1}{2}\)
TH1: \(5-3x=-\dfrac{1}{2}\Rightarrow3x=\dfrac{11}{2}\Rightarrow x=\dfrac{11}{6}\)
TH2: \(5-3x=\dfrac{1}{2}\Rightarrow3x=\dfrac{9}{2}\Rightarrow x=\dfrac{3}{2}\)
giúp mik giải 2 bài này vs ạ
