There is a mistake in the following statement: 1. Any rational number has reciprocal; 2. The product of two reciprocal numbers is 1.3. The sign of two reciprocal numbers is the same Another is that 1 and negative 1 are reciprocal

There is a mistake in the following statement: 1. Any rational number has reciprocal; 2. The product of two reciprocal numbers is 1.3. The sign of two reciprocal numbers is the same Another is that 1 and negative 1 are reciprocal

1 error 0 has no countdown
That's right
Three pairs of a * 1 / a = 1, a and 1 / a have the same sign
1 * (- 1) = - 1 of 4 pairs

Does any rational number have a reciprocal?

No, 0 is not countdown

Is the reciprocal of a non-zero rational number necessarily a rational number

Yes

Is the reciprocal of a rational number necessarily a rational number?

Not necessarily
0 is a rational number
He didn't count down

If there are only four Sundays in March, then March 1 can't be the day of the week. There is something to calculate

It can't be Friday, Saturday or Sunday. If the 1st is Saturday, there will be five Sundays in March, and the fifth Sunday is the 30th of this month; if the 1st is Sunday, the fifth Sunday is the 29th of this month; if the 1st is Friday, the fifth Sunday is the 31st of this month

Shrek, the monster, has found four strange formulas. There is not a single number among them. He just knows that a, B, C, D, e and f represent one of the numbers 0, 1, 2, 3, 4 and 5. Please help me figure out which letter is 012345?
A+B=A
C×E=C
C-D=E
F÷D=D

B=0
E=1
F=4
D=2
C=3
A=5

1001 × (5 and 5 / 13) + 198 ÷ (198 and 198 / 199) + 1 and 1 / 200

5392

There is a probability formula in high school mathematics, which is a pen standing up and then falling down. The formula reflecting probability is from little knowledge
What's the formula? How did it come from? This formula was invented by a foreigner. It's very famous. How can it be proved? It's not a summary of probability, is it

In the 18th century, French mathematicians Buffon and leclere put forward the "needle throwing problem", which was recorded in Buffon's works published in 1777: "draw a group of parallel lines with a distance of D on the plane, and draw a length of L (L) on the plane

What is the result of equation [(x + 52.9) * 5-3.9343] / 0.5-10x = 521.1314?
Please list the steps to solve the problem

[(x + 52.9) * 5-3.9343] / 0.5-10x = 521.1314 (5x + 264.5-3.9343) / 0.5-10x = 521.13145x / 0.5 + 264.5 / 0.5-3.9343 / 0.5-10x = 521.131410x + 529-7.8686-10x = 521.131410x-10x + 529-7.8686 = 521.1314529-7.8686 = 521.1311314, we can see that: X passes through

How about 4x out of 5-6x out of 7 = 12

4X / 5-6x / 7 = 12
Multiply both sides by 35
28x-30x=420
-2x=420
x=420÷（-2）
x= -210
You can ask if you don't understand! Thank you!
I wish you progress in your study!