A rule "*" is defined as follows: a * b = {a (a > b) B (a ≤ b), for example, 1 * 2 = 2, if (- 2m-5) * 7 = 7 Then the value range of M is ()

A rule "*" is defined as follows: a * b = {a (a > b) B (a ≤ b), for example, 1 * 2 = 2, if (- 2m-5) * 7 = 7 Then the value range of M is ()

From the problem: - 2m-5 ≤ 7, we can get - 6 ≤ M

What do you mean when a equals B and a equals B?

A intersects B, that is, take the small one between a and B. A and B take the big one between a and B. because a is equal, a = B

The second power of 1x3 = 3 = 2-1,3x5 = 15 = 4-1,5x7 = 35 = 6-1
What is the nth formula?

The nth formula is (2n-1) (2n + 1) = 4N ^ 2-1

What rules do you find by observing the following? 3 × 5 = 15, 15 = 42-15 × 7 = 35, and 35 = 62-1 11 × 13 = 143, and 143 = 122-1 Express the law of your conjecture with an algebraic expression containing only one letter N, and find the value of the algebraic expression when n = 21

3×5=（4-1）（4+1）=42-1，5×7=（6-1）（6+1）=62-1… 11×13=（12-1）（12+1）=122-1，… So the nth formula is: (2n-1) (2n + 1) = (2n) 2-1; substitute n = 21 into (2n) 2-1 = 1763

3x5 = 15 and 15 = 4x4-1, 5x7 = 35 and 35 = 6x6-1 11x13 = 143 and 143 = 12x12-1 will give you the rule of conjecture

N*(N+2)=(N+1)2-1

1. Let s = 2 / 1x3 + 2 squared / 3x5 + ·· + 2 49th power / 97x99,
T = 1 / 3 + 2 / 5 + 2 squared / 7 + ····· + 2 48th power / 99, then S-T = () a, 2 49th power. B, 1 - (2 29th power / 99) C, 2 49th power-1d, 2 49th power + 1

S=2/1*3+2^2/3*5+...+2^49/97*99=(1-1/3)+2(1/3-1/5)+2^2(1/5-1/7)+...+2^48(1/97-1/99)=1-1/3+2/3-2/5+2^2/5-2^2/7+...+2^48/97-2^48/99;S-T=1-2*1/3+2*1/3-2^2/5+2^2/5-2^3/7+2^3/7-...-2^48/97+2^48/97-2^49/99;=...

Look at the following test and write the 40th formula: 1 + 2, 2 + 5, 3 + 8, 1 + 11, 2 + 14, 3 + 17

First find the first addend:
Law: 1,2,3 cycle, so the fortieth is 1
Second addend:
The law is 3 * X-1, and X is the number one
The fortieth formula is 3 * 40 - 1 = 119
So it is
1+119

Given 1 + 2 + 3 + 4 + ··· + 33 = 17 * 33, calculate 1-3 + 2-6 + 3-9 + 4-12+·····

Take a look at the calculation process, 1 + 2 + 3 + 4 = [1x2 + 2x (3-1) + 3x (4-2) + 4x (5-3)] / 2 = [1x2 - 1x2 + 2x3 - 2x3 + 3x4 - 3x4 + 4x5] / 2 = 4x5 / 2, so 1 + 2 + 3 + 4 + +33 = 33 x 34 / 2 = 17 x 33 the same as 1 - 3 + 2 - 6 + 3 - 9 + 4

When Xiaohua calculates a decimal addition, he takes 8 on the tenth place of an addend as 3, and 1 on the hundredth place of another addend as 7. The result is 20.8. What is the correct result?

Correct is 20.8 + 0.1 × (8-3) - 0.01 × (7-1)
=20.8+0.5-0.06
=21.24；

In the calculation of an addition, the number 5 on the tenth digit of an addend is regarded as 3, the number 7 on the hundredth digit of another addend is regarded as 2, and the sum is 852
It's going to be the best

Correct result = 852 + 20 + 500 = 1372
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