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6.(5x+35)=330
5x+35 =330:6
5x+35 = 55
5x = 55-35
5x = 20
x = 20:5
x = 4
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-472 + (235 - 28) - 35 - 350
= -472 + 207 - 35 - 350
= -265 - 35 - 350
= 300 - 350 = -50
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`Answer:`
\(S=\frac{1}{14}+\frac{1}{35}+\frac{1}{65}+...+\frac{1}{350}\)
\(\Rightarrow S=\frac{2}{28}+\frac{2}{70}+\frac{2}{130}+...+\frac{2}{700}\)
\(\Rightarrow S=\frac{2}{4.7}+\frac{2}{7.10}+\frac{2}{10.13}+...+\frac{2}{25.28}\)
\(\Rightarrow S=\frac{2}{3}\left(\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+...+\frac{1}{25.28}\right)\)
\(\Rightarrow S=\frac{2}{3}\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+...+\frac{1}{25}-\frac{1}{28}\right)\)
\(\Rightarrow S=\frac{2}{3}.\frac{3}{14}\)
\(\Rightarrow S=\frac{1}{7}\)
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a: -127+208-73+92
\(=\left(-127-73\right)+\left(208+92\right)\)
\(=300-200=100\)
b: \(-46+391+246-691\)
\(=\left(-46+246\right)+\left(391-691\right)\)
\(=200-300=-100\)
c: \(-472+\left(235-28\right)-\left(35-350\right)\)
\(=-472+235-28-35+350\)
\(=\left(-472-28\right)+350+\left(235-35\right)\)
\(=-500+350+200=50\)
a) -127+208-73+92
=(−127−73)+(208+92)
=300−200
=100
b) −46+391+246−691
=(−46+246)+(391−691)
=200−300
=−100
c) −472+(235−28)−(35−350)
=−472+235−28−35+350
=(−472−28)+350+(235−35)
=−500+350+200
=50
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
-472 + (235 - 28) - (35 - 350)
= -472 + 235 - 28 - 35 + 350
= (-472 - 28) + (235 - 35) + 350
= -500 + 200 + 350
= -500 + 550
= 50
đề có bị sai k bn?
6. [5x +35] = 360
5s+35=360:6
5x-35=60
5x=60+35
5x=95
x=95:5
x=19