What can be calculated simply is 24 × (2 / 3-1 / 4 + 5 / 12)

What can be calculated simply is 24 × (2 / 3-1 / 4 + 5 / 12)

24×（2/3－1/4+5/12）
=24×（2/3)－24×（1/4）+24×(5/12）
=16 - 6+10
=20

Sum Sn = 1 ^ 2 + 3 ^ 2 + 5 ^ 2 + 7 ^ 2 + +(2n-1)^2

1^2+2^2+3^3+...+n^2=n(n+1)(2n+1)/6
(2n)^2-(2n-1)^2=4n-1
2^2+4^2+6^2+.(2n)^2-[1^2+3^2+5^2+.(2n-1)^2]
=4(1+2+3+...+n)-n
=2n(n+1)-n=n(2n+1)
2[1^2+3^2+.+(2n-1)^2]+n(2n+1)=2n(2n+1)(4n+1)/6
1^2+3^2+5^2+.+(2n-1)^2=n(2n-1)(2n+1)/3
This problem is very good. I'm very happy to deduce it and verify it

What are the monotone decreasing and monotone increasing intervals of the function y = | 1 + 2x | + | 2-x |?
Why?

Let 1 + 2x = 0,2-x = 0
That is, x = - 1 / 2, x = 2
When - ∞

The greatest common divisor of two numbers is 6 and the least common multiple is 36. These two numbers can be () and () or () and ()

6 and 36 12 and 18

The square of a plus the square of B equals 1, the square of B plus the square of C equals 2, the square of a plus the square of C equals 2. What is the minimum value of AB + BC + AC

Let y = 1 / (x ^ 2 + 3x + 2), find the n-order derivative of Y
The answer is [(- 1) ^ n] n! [1 / (x + 1) ^ (n + 1) - 1 / (x + 2) ^ (n + 1)]

Simplification of the original formula y = 1 / (x + 1) - 1 / (x + 2)
So its n-order derivative is (- 1) ^ n / (x + 1) ^ (n + 1) + (- 1) ^ (n-1) / (x + 2) ^ (n + 1)

(- 3 and two thirds) + (- 2.4) - (- 1 / 3) - (- 4 and two fifths) how to do this problem? Please use a simple method
And teach me why?

First make sure the sign, negative sign can be taken out, pay attention to negative get positive, that is: - 3 and 2 / 3-2.4 + 1 / 3 + 4 and 2 / 5
Then the decimal is converted into a fraction, 2.4 is 2 and 2 / 5, that is: - 3 and 2 / 3-2 and 2 / 5 + 1 / 3 + 4 and 2 / 5
Then put the same denominator together. Generally, the positive ones are put in the front and the negative ones are put in the back,
That is: 1 / 3-3 and 2 / 3 + 4 and 2 / 5-2 and 2 / 5 = - 3 and 1 / 3 + 2 = - 1 and 1 / 3

What is the sum of the reciprocal of one and two-thirds plus 1.25 divided by one-third
Urgent

One and two thirds is 5 / 3, the reciprocal is 3 / 5; 1.25 is 5 / 4, 1.25 is divided by one third, 1 / 3 △ 5 / 4 = 4 / 15
1/（1+2/3）+1/3÷5/4
=3/5+4/15
=13/15
=13:15

How to solve 2x + 2 = 3x-3

For example: 2x + 2 = 3x-3
2x-3x=-3-2
(2-3) x = - 5, that is - x = - 5
So we get x = 5
Set into the above question is: 2 * 5 + 2 = 3 * 5-3, that is 12 = 12 correct!

Simple calculation of 1997 * 0.3/1999 * 0.5 + 1.2/1999
*I'll offer a reward to 10 wealth (of course, it's better) for Chenghao,

1997*0.3/1999*0.5+1.2/1999
=1997*0.3/1999*0.5+1.2*0.5/1999*0.5
=（1997*0.3+1.2*0.5）/1999*0.5
=（1997*0.3+0.3*2）/1999*0.5
=0.3*1999/1999*0.5
=3/5
Remember to give points