85.(-5)8+(-2)5.109/216.57+218
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Đáp án A
Độ lớn điện tích mỗi hạt bụi:
5 . 10 9 . 1 , 6 . 10 - 19 = 8 . 10 - 10 C .
Lực tương tác Cu lông
F = k q 1 q 2 r 2 = 9 . 10 9 8 . 10 - 10 2 0 , 02 2 = 1 , 44 . 10 - 5 N
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\(218-5\cdot(x+8)=2^2\\\Rightarrow 218-5\cdot(x+8)=4\\\Rightarrow 5\cdot(x+8)=218-4\\\Rightarrow 5\cdot(x+8)=214\\\Rightarrow x+8=214:5\\\Rightarrow x+8=42,8\\\Rightarrow x=42,8-8\\\Rightarrow x=34,8\)
⇒218-5*(x+8)=4
⇒5*(x+8)=218-4
⇒5*(x+8)=214
⇒x+8=214:5
⇒x+8=42,8
⇒x=34,8
⇒x
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tìm x :
200 -(2 . x + 6) = 64
2 . x + 6 = 200 - 64
2 . x + 6 = 136
2 . x = 136 - 6
2 . x = 130
x = 130 : 2 = 65
Tính nhanh
1972 - (368 +972)
1972 - 1340
= 632
3345 - 1000 : 192 - 2 . (221 - 218 ) . 3
3345 - ( 1000 ko chia hết cho 192 )
999 + 85 = 1084
( 1 + 37) x 37 : 2 = 703
( 1 + 2017) x 2017 : 2 = 2035153
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Ta có : 148 : (x + 2) = 378
=> x + 2 = 148 : 378
=> x + 2 = 74/189
=> x = 74/189 - 2
=> x= -304/189
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a.
\(\left[3\times\left(-2\right)-\left(-8\right)\right]\times\left(-7\right)-\left(-2\right)\times\left(-5\right)=\left(-6+8\right)\times\left(-7\right)-10=2\times\left(-7\right)-10=-14-10=-24\)
b.
\(85\times\left(35-27\right)-35\times\left(85-27\right)=85\times35-85\times27-35\times85+35\times27=\left(85\times35-35\times85\right)-27\times\left(85-35\right)=-27\times50=-1350\)
c.
\(\left(20\times2^4-12\times2^3-48\times2^2\right)^2\div\left(-8\right)^2=\left(\frac{5\times4\times2^4-3\times4\times2^3-3\times16\times2^2}{-8}\right)^2=\left(\frac{5\times2^2\times2^4-3\times2^2\times2^3-3\times2^4\times2^2}{\left(-2\right)^3}\right)^2\)\(=\left(\frac{2^5\times\left(5\times2-3-3\times2\right)}{-\left(2^3\right)}\right)^2=\left(-2^2\right)^2=16\)
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\(2^3-5^3:5^2+12\cdot2^2=8-5+48=51\\ 5\left[\left(85-35:7\right):8+90\right]-5\cdot2^2\\ =5\left(80:8+90\right)-20=5\cdot100-20=480\)