100 x 39 + 39 - 15 x 10
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10 x 10 = 100.
10 x 20 = 200.
50 x 10 = 500.
10 x 39 = 390.
#Trang
#Fallen_Angel

a) \(5+3^{x+1}=86\)
\(=>3^{x+1}=86-5\)
\(=>3^{x+1}=81=3^4\)
\(=>x+1=4\) ( cùng cơ số )
\(=>x=4-1\)
\(=>x=3\)
b) \(15:\left(x+2\right)=\left(3^3+3\right):10\)
\(=>15:\left(x+2\right)=\left(27+3\right):10\)
\(=>15:\left(x+2\right)=30:10=3\)
\(=>x+2=15:3\)
\(=>x+2=5\)
\(=>x=5-2\)
\(=>x=3\)
c) \(\left(9x+2\right).4=80\)
\(=>9x+2=80:4\)
\(=>9x+2=20\)
\(=>9x=20-2\)
\(=>9x=18\)
\(=>x=18:9\)
\(=>x=2\)
d) \(\left(245-x\right)+7^2=14\)
\(=>\left(245-x\right)+14=14\)
\(=>245-x=14-14\)
\(=>245-x=0\)
\(=>x=245-0\)
\(=>x=245\)


a) 92 : 0,01 = 9200 92 x 100 = 9200 64 : 0,01= 6400
b) 25 : 0,5 = 50 25 x 2 = 50 39 : 0,5 = 78
c) 32 : 0,25 = 128 32 x 4 = 128 15 : 0,25 = 60

x.(\(\dfrac{1}{6}\)+\(\dfrac{1}{10}\)+\(\dfrac{1}{15}\)+\(\dfrac{1}{21}\)+\(\dfrac{1}{28}\)+\(\dfrac{1}{36}\)+\(\dfrac{1}{45}\)+\(\dfrac{1}{55}\)+\(\dfrac{1}{66}\)+\(\dfrac{1}{78}\))=\(\dfrac{220}{39}\)
x.\(\dfrac{20}{39}\)=\(\dfrac{220}{39}\)
x=\(\dfrac{220}{39}\):\(\dfrac{20}{39}\)
x=11

1: =-2/9(15/17+2/17)=-2/9
2: \(=\dfrac{-6}{3}+\dfrac{-21}{90}\)
=-2-7/30=-67/30
3: \(=\dfrac{3}{4}\cdot\dfrac{7}{5}+\dfrac{9}{7}\cdot\dfrac{3}{2}\)
=21/20+27/14=417/140
4: =-25/13(5/19+14/19)=-25/13
5: =-7/5-45/21=-7/5-15/7=-124/35
1: =-2/9(15/17+2/17)=-2/9
2: =−63+−2190=−63+−2190
=-2-7/30=-67/30
3: =34⋅75+97⋅32=34⋅75+97⋅32
=21/20+27/14=417/140
4: =-25/13(5/19+14/19)=-25/13
5: =-7/5-45/21=-7/5-15/7=-124/35

x.(1/6+1/10+1/15+1/21+1/28+1/36+1/45+1/55+1/66+1/78)=220/39
x.20/39=220/39
x=220/39:20/39
x=11

6x+10x+15x+21x+28x+36x+45x+55x+66x+78x+78x=39220
\(\Leftrightarrow x \left(\right. \frac{1}{6} + \frac{1}{10} + \frac{1}{15} + \frac{1}{21} + \frac{1}{28} + \frac{1}{36} + \frac{1}{45} + \frac{1}{55} + \frac{1}{66} + \frac{1}{78} + \frac{1}{78} \left.\right) = \frac{220}{39}\)
\(\Leftrightarrow x \cdot \frac{20}{39} = \frac{220}{39} \Rightarrow x = 11\) day nha
3789
\(100\cdot39+39-15\cdot10\)
\(=39\cdot\left(100+1\right)-150\)
\(=39\cdot101-150\)
=3939-150
=3789