If a and B satisfy a + B = 3 and A-B = 2, then A-B = ()

A-B = (a + b) (a-b) = 3x2 = 6
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If rational numbers a and B satisfy a + √ 2 = 3 + B √ 2, then a= b=

How much current can a 1.5 square meter wire withstand?

There is a formula to calculate, and there is also a formula to sum up experience. Generally, 1.5 can withstand the current of about 9a, and the current carrying capacity of copper wire is 1.5-2 times that of aluminum wire. Lvlujiayuan's answer is correct. The key to using electricity is safety. Considering the increase of electrical appliances in the future, there is no harm in having a larger wire diameter, and there is no need to be too large. It depends on what you do. The formula is: 6 in 10, 4 in 10, 3 in 100, half of aluminum wire, This is the safest safety data. As long as 1.5 is no more than 10a, there is no problem. I don't know if I'm clear. If I don't understand, I'm sorry I can't say it clearly. You can ask me again, hoping to help you. By the way, the number behind the formula is coefficient, 1.5 * 6 = 9, 2.5 * 6 = 15

7 (A-1) + X (A-1) and 3 (a-b) & # 178; + 6 (B-A) and 2 (m-n) & # 178; - M (m-n) and X (X-Y) & # 178; - Y (Y-X) & # 178;
And m (A & # 178; + B & # 178;) - na & # 178; - NB & # 178;

7（a-1）+x（a-1）
=（x+7）(a-1);
3（a-b）²+6（b-a）
=3(a-b)(a-b-2);
2（m-n）²-m（m-n)
=(m-n)(2m-2n-m)
=(m-n)(m-2n);
x（x-y）²-y（y-x)²
=(x+y)(x-y)²;
m（a²+b²）-na²-nb²
=(m-n)(a²+b²)
I'm very glad to answer your questions. Skyhunter 002 will answer your questions
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Excuse me: how many kilowatt hours of electricity does a 15 Watt electrical appliance use for 24 hours in a month?
And: how is it calculated?

One kilowatt hour is 1000 watt hours
A day is 15 watts * 24 hours = 360 watt hours
January is 360 watt hours * 30 = 10800 watt hours
If you change it to a few kilowatts, 10800 / 1000 = 10.8 kilowatts
See?

Probability and statistics high school mathematics problems
In order to control the infection of a certain virus, the epidemic prevention department of the Ministry of health of a city provided five batches of vaccines with batch numbers of 1, 2, 3, 4 and 5 respectively for the citizens of a, B and C districts under the jurisdiction of the city to inject. Each district can choose one batch of vaccine from them. (1) calculate the probability that the vaccine batch numbers injected in the three districts are different from each other; (2) record that the maximum number of vaccine batch numbers selected in a, B and C districts is K, Find the expectation of K
The answer is more detailed
P(K=2)=(3+3+1)/125=7/125
P(K=3)=(6+34+1)/125=19/125
P(K=4)=(36+36+1)/125=37/125
P(K=5)=(66+38+1)/125=61/125
What do 3 + 3 + 1 mean? I don't understand. Please explain
I understand a little bit 6 + 3 4 + 1. Let's explain this again. Thank you

1)(5*4*3)/(5*5*5)=48%
2)p(k=1)=1/(5*5*5)=1/125
p(k=2)=C(3,1)*1/5*(1/5)^2+C(3,2)*(1/5)^2*1/5+C(3,3)*(1/5)^3=7/125
p(k=3)=C(3,1)*1/5*(2/5)^2+C(3,2)*(1/5)^2*2/5+C(3,3)*(1/5)^3=19/125
p(k=4)=C(3,1)*1/5*(3/5)^2+C(3,2)*(1/5)^2*3/5+C(3,3)*(1/5)^3=37/125
p(k=5)=C(3,1)*1/5*(4/5)^2+C(3,2)*(1/5)^2*4/5+C(3,3)*(1/5)^3=61/125
p(k=5)=C(3,1)*1/5*(4/5)^2+C(3,2)*(1/5)^2*4/5+C(3,3)*(1/5)^3=61/125
C (3,1) C (3,1) * 1 / 5 * (4 / 5) ^ 2 means that k = 5 has been selected once, and the other two districts are No. 1 to No. 4 vaccines,
C (3,2) * (1 / 5) ^ 2 * 4 / 5 means that k = 5 has been selected twice, and the other one is vaccine No. 1 to 4
C (3,3) * (1 / 5) ^ 3 indicates that No. 5 vaccine has been used in all districts
So e (k) = 1 / 125 + 2 * 7 / 125 + 3 * 19 / 125 + 4 * 37 / 125 + 5 * 61 / 125 = 4.2

How is the concept of energy and the unit of Joule established?
Why is the result of force and displacement linked to energy?
Product of force and displacement
Only conclusions and results are written in textbooks. I only know how to do questions, but I don't really understand them. I feel empty.
I want to know the research process of our ancestors at that time.

1J is the amount of work done in 1 second at 1 W power
Work is the accumulation of force in space
You study physics very seriously, love to study, I hope you study hard

Calculation: 14 / 15 × (5 / 14 + 5 / 21) + 2 / 3

14/15×(5/14+5/21)+2/3
=14/15×5/14+14/15×5/21+2/3
=1/3+2/9+2/3
=1 and 2 / 9

The invention of Volta~
Four

Volt finally got the idea that he connected some of the first and second conductors so that the potential differences at each contact point could be added up, In a famous letter to the president of the Royal Society, banks (1743-1820), he introduced his invention with the title "on electricity generated by contact of different conductive substances". The stack can produce continuous current, and its intensity is orders of magnitude larger than that obtained from an electrostatic starter, Thus began a real scientific revolution
In 1801, he went to Paris to perform his experiment at the French Academy of Sciences. Napoleon was also present at that time. He immediately ordered that volt be awarded a special gold medal and a pension, so volt became Napoleon's protector, just as he did 20 years ago, He used to be the patron of Emperor Joseph II of Austria. When he asked to resign from the University of Pavia and retire in 1804, Napoleon refused his request, granted him more fame and money, and granted him the title of earl. He did not care about politics, but only focused on his research
He may be too old to compete with the young new force, or he may be psychologically hindered by his great achievements before. He has never left school, and his work may be too personal, The lack of formal mathematics in his writings and teaching may have limited his ability to express his thoughts. Volt spent his last eight years in his villa cannagol and near Como, and he lived a life of complete seclusion. In 1827, he died at the age of 82

3 / 5 △ [(3 / 8 + 1 / 2) × 7 / 9]

=3 / 5 ^ [7 / 8 ^ 7 / 9]
=3 / 5 ÷ [7 / 8 times 9 / 7]
=3 / 5 ／ 9 / 8
=3 / 5 times 8 / 9
=8 out of 15
Jack up

If a and B satisfy a + B = 3 and A-B = 2, then A-B = ()