5+5+10+80-1=
?
Tính nhẩm:
80 + 10 = 30 + 40 = 80 + 5 =
90 - 80 = 70 - 30 = 85 - 5 =
90 - 10 = 70 - 40 = 85 - 80 =
80 + 10 = 90 30 + 40 = 70 80 + 5 = 85
90 - 80 = 10 70 - 30 = 40 85 - 5 = 80
90 - 10 = 80 70 - 40 = 30 85 - 80 = 5
80+10=90 30+40=70 80+5=85
90-80=10 70-30=40 85-5=80
90-10=80 70-40=30 85-80=5
80 + 10 = 90 30 + 40 = 70 80 + 5 = 85
90 - 80 = 10 70 + 30 = 90 85 - 5 = 80
90 - 10 = 80 70 - 40 = 30 85 - 80 = 5
10. 2 1/2 x 7/5 + {-9/10} x 2/3
11. X + 45% = 2 1/2 -5/3
12. 80% + X = -5/2 + 3/4
13. 4/25 - X =-5/2 + -3/10
`2 1/2 xx 7/5 + (-9/10) xx 2/3`
`= 5/2 xx 7/10 + (-9/10) xx 2/3`
`= 35/20 + (-18/30)`
`= 7/4 + (-3/5)`
`= 23/20`
__
`x + 45% =2 1/2 - 5/3`
`=> x+ 45/100 = 5/2 - 5/3`
`=>x+ 9/20= 15/6-10/6`
`=> x+9/20 = 5/6`
`=>x= 5/6 - 9/20`
`=>x=23/60`
__
`80% +x=-5/2 +3/4`
`=> 80/100 + x= -10/4 +3/4`
`=> 4/5 + x= -7/4`
`=>x= -7/4-4/5`
`=>x=-51/20`
__
`4/25 -x=-5/2 +(-3/10)`
`=> 4/25 -x= -25/10 +(-3/10)`
`=> 4/25 -x= -28/10`
`=>x= 4/25 -(14/5)`
`=>x= 4/25 + 14/5`
`=>x=74/25`
1+1+2+3+4+5+6+7+8+9+10+10+10+10+80+90=?
1 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 10 + 10 + 10 + 80 + 90
= ( 1 + 5 ) + ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + ( 10 + 90 ) + ( 10 + 10 + 80 ) + 10
= 6 + 10 + 10 + 10 +10 + 100 + 100 + 10
= 16 + 10 + 10 + 10 + 100 + 100 + 10
= 26 + 10 + 10 + 100 + 100 + 10
= 36 + 10 + 100 + 100 + 10
= 46 + 100 + 100 + 10
= 146 + 100 + 10
= 246 + 10
= 256
Chúc bạn hok tốt !
\(a,80-\left(10x-5\right)=45\\ \Rightarrow80-10x+5=45\\ \Rightarrow-10x=-40\\ \Rightarrow x=4\)
\(b,\left(x+1\right)\left(x-2\right)=0\\ \Rightarrow\left[{}\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
\(c,\left|5+5x\right|=2^2.5\\ \Rightarrow\left|5+5x\right|=20\\ \Rightarrow\left[{}\begin{matrix}5+5x=20\\5+5x=-20\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}5x=15\\5x=-25\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\)
\(d,-10-\left(-5\right)+\left(3-x\right)=-8\\ \Rightarrow-10+5+3-x=-8\\ \Rightarrow-x=-6\\ \Rightarrow x=6\)
a) 80-(10x-5)=45
=> 80 - 10 x + 5 =45
=>-10x = -40
=>x=4
b)(x+1)×(x-2)=0
\(\Rightarrow\left[{}\begin{matrix}x+1=0\\x=2+0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
c) |5+5x|=2^2×5
=>|5+5x|=20
\(\Rightarrow\left[{}\begin{matrix}5+5x=-20\\5+5x=20\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-5\\x=3\end{matrix}\right.\)
d) -10-(-5)+(3-x)=-8
=>-10+5 +3-x=-8
=>2+x=8
=>x=6
C= 1/5+1/10+1/20+1/40+1/80+...........+1280
C = \(\frac{1}{5}\)+\(\frac{1}{10}\)+\(\frac{1}{20}\)+\(\frac{1}{40}\)+\(\frac{1}{80}\)+........+\(\frac{1}{1280}\)
2C = 2 . ( \(\frac{1}{5}\)+\(\frac{1}{10}\)+.......+\(\frac{1}{1280}\))
2C = \(\frac{2}{5}\)+\(\frac{1}{5}\)+\(\frac{1}{10}\)+.....+\(\frac{1}{1280}\)
2C-C = ( \(\frac{2}{5}\)+\(\frac{1}{5}\)+\(\frac{1}{10}\)+......+\(\frac{1}{1280}\)) - (\(\frac{1}{5}\)+\(\frac{1}{10}\)+.....+\(\frac{1}{1280}\))
C . ( 2-1) = \(\frac{2}{5}\)
C = \(\frac{2}{5}\)
Vậy C = \(\frac{2}{5}\)
\(C=\frac{1}{5}+\frac{1}{10}+\frac{1}{20}+\frac{1}{40}+\frac{1}{80}+........+\frac{1}{1280}\)
\(\Rightarrow2C=2\left(\frac{1}{5}+\frac{1}{10}+\frac{1}{20}+\frac{1}{40}+\frac{1}{80}+...........+\frac{1}{1280}\right)\)
\(\Rightarrow2C=\frac{2}{5}+\frac{1}{5}+\frac{1}{10}+.............+\frac{1}{1280}\)
\(\Rightarrow2C-C=\left(\frac{2}{5}+\frac{1}{5}+\frac{1}{10}+............+\frac{1}{1280}\right)-\left(\frac{1}{5}+\frac{1}{10}+\frac{1}{20}+\frac{1}{40}+\frac{1}{80}+...........+\frac{1}{1280}\right)\)
\(\Rightarrow C=\frac{2}{5}-\frac{1}{1280}\)
\(\Rightarrow C=\frac{512}{1280}-\frac{1}{1280}\)
\(\Rightarrow C=\frac{511}{1280}\)
Vậy C = \(\frac{511}{1280}\)
1/5+1/10+1/20+1/40+1/80+..+1//320+1/640
Bài 3: Viết tiếp 5 số trong dãy sau. a) 5, 10, 20, 40, 80, …………………………………. b) 1, 2, 3, 5, 8, 13, …………………………………… c) 1, 3, 11, 47, ……………………………………….
a) 5, 10, 20, 40, 80, 160, 320, 640, 1280, 2560
b) 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144
c 1, 3, 11, 47,
1/5+1/10+1/20+1/40+1/80+1/160
hướng dẫn em nhé:
quy đồng mẫu số lên có mẫu số chung là 160 rồi cộng lại em nhé
3) Tìm x của N biết a) 80 - ( 2 + 2x ) : 2 = 40 b) 11^2 - 121 = 0 c) 5^x+3 - 7 × 5^2 = 5^2 × 18 d) x^10 = x e) x^10 = 1^x g) ( 2x - 15 )^5 = ( 2x - 15 )^3 4) Thực hiện phép tính a) 5^3 ÷ 5^2 + 2^2 × 3 b) 4^3 × 125 - 125 ÷ 5^2 c) 6^2 × 28 + 72 × 6^2 d) 5^6 ÷ 5^4 + 3 × 3^2 - 80 e) 2^3 × 19 - 2^3 × 14 × 1^2021