Tìm x,Biết
2.x+3=8
x:5-2=3
x:7-2=19
(x+3)x2=18
20-(x+3)=5
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\(2x+3=8\)
\(\Rightarrow2x=8-3\)
\(\Rightarrow2x=5\)
\(\Rightarrow x=5:2\)
\(\Rightarrow x=\dfrac{5}{2}\)
\(\dfrac{14}{15}=1-\dfrac{1}{15};\dfrac{15}{16}=1-\dfrac{1}{16};\dfrac{16}{17}=1-\dfrac{1}{17};\dfrac{17}{18}=1-\dfrac{1}{18}\\ Vì:\dfrac{1}{15}>\dfrac{1}{16}>\dfrac{1}{17}>\dfrac{1}{18}\\ Nên:1-\dfrac{1}{15}< 1-\dfrac{1}{16}< 1-\dfrac{1}{17}< 1-\dfrac{1}{18}\\ Vậy:\dfrac{14}{15}< \dfrac{15}{16}< \dfrac{16}{17}< \dfrac{17}{18}\\ P.s.lớn.nhất:\dfrac{17}{18}\)
14.25.6.7
= 2.7.25.2.3.7
= (2.2.25).(7.7.3)
= 100.(7.21)
= 100.147
= 14700
15.6.4.125.8
= (15.4.6).(125.8)
= (60.6).1000
= 360.1000
= 360 000
15.6.4.125.8
=(15.4.6).(125.8)
=(60.6).1000
=360.1000
=360000
b) \(\sqrt{\dfrac{1-\sqrt{3}}{1+\sqrt{3}}+\sqrt{\dfrac{2+\sqrt{3}}{2-\sqrt{3}}}}\)
\(=\sqrt{\dfrac{1-\sqrt{3}}{1+\sqrt{3}}+\sqrt{\dfrac{4+2\sqrt{3}}{4-2\sqrt{3}}}}\)
\(=\sqrt{\dfrac{1-\sqrt{3}}{1+\sqrt{3}}+\dfrac{\sqrt{3}+1}{\sqrt{3}-1}}=\sqrt{\dfrac{\left(\sqrt{3}+1\right)^2-\left(\sqrt{3}-1\right)^2}{\left(\sqrt{3}-1\right).\left(\sqrt{3}+1\right)}}\)
\(=\sqrt{\dfrac{4\sqrt{3}}{2}}=\sqrt{2\sqrt{3}}\)
125.98.2.8.25
= (125.8).49.2.2.25
= 1000.49.100
= 4 900 000
0,9.95+ 1,8.2 + 0,9
= 0,9.95 + 0,9. 2.2 + 0,9.1
= 0,9.(95+4+1)
= 0,9.100
= 90
\(2x+3=8\)
\(\Rightarrow2x=8-3\)
\(\Rightarrow2x=5\)
\(\Rightarrow x=\dfrac{5}{2}\)
\(x:5-2=3\)
\(\Rightarrow x:5=3+2\)
\(\Rightarrow x:5=5\)
\(\Rightarrow x=5\cdot5\)
\(\Rightarrow x=25\)
\(x:7-2=19\)
\(\Rightarrow x:7=19+2\)
\(\Rightarrow x:7=21\)
\(\Rightarrow x=21\cdot7\)
\(\Rightarrow x=147\)
Mình chưa rõ đề
\(20-\left(x+3\right)=5\)
\(\Rightarrow-x-3=5-20\)
\(\Rightarrow-x-3=-15\)
\(\Rightarrow-x=-15+3\)
\(\Rightarrow-x=-12\)
\(\Rightarrow x=12\)