13 divided by 9, then divided by 0.5625, then - 9 out of 8, hurry, hurry All kinds of demands, who can add ten

13 divided by 9, then divided by 0.5625, then - 9 out of 8, hurry, hurry All kinds of demands, who can add ten

13 divided by 9, then divided by 0.5625, and then -- 9 out of 8
=13 / 9 times 0.5625 -- 9 / 8
=13 times 0.625 -- 9 / 8
=13 times 5 / 8 -- 9 / 8
=65/8--9/8
=56/8
=7.

How to find the limit of (2 ^ x-1) / X when x approaches 0?
There are two important limits
Let: 2 ^ X - 1 = t, then: x = ln (1 + T) / LN2, X - > 0, T - > 0
lim(x->0) (2^x-1)/x
=lim(x->0) t/[ln(1+t)/ln2]
=lim(x->0) ln2/ln[(1+t)^(1/t)]
= ln2/lne
= ln2
How did ln [(1 + T) ^ (1 / T)] come from?
I can't be too detailed. I'm poor at math

(31.6-11.7) / 2.5/0.4

（31.6-11.7）÷2.5÷0.4
=（31.6-11.6-0.1）÷（2.5×0.4）
=（20-0.1）÷1
=19.9

Factoring a problem
The square of 2n-15n-50 = 0
How to ask? Yes,

(2n + 5) (N-10) = 0 cross multiplication

How to calculate 52 × 0.99?
52×0.99
How to simplify this problem

52×0.99
=52×（1-0.01）
=52×1-52×0.01
=52-0.52
=51.48

Given that a straight line L passes through point a (- 1, - 3), its inclination angle is equal to 2 times of the inclination angle of the straight line y = 3 times X,

Let the equation of line l be y = KX + B, because the slope of the line y = 3 times x is 3, the inclination angle is 30 degrees, and Tan 30 = 3. So the inclination angle of the equation of line L is 60, and the slope is Tan 60 = 3, that is to say, k = 3. Bring it and the coordinates of point a into y = KX + B, and then find B

Solution equation: (5x-1) divided by 6 = 7 / 3

Double six on both sides
5x-1=14
5x=14+1
5x=15
x=15÷5
x=3

The equation system x + Y-2 = 0,2x-3y + 6 = 0, the number of elements in the set composed of solutions is

x+y-2=0 ①
2x-3y+6=0 ②
① When y is eliminated, we get: 5x = 0, so x = 0
Substituting into ①, we get Y-2 = 0, y = 2
So x = 0, y = 2
That is, the set of solutions is {(0,2)}, with only one element

Simple calculation of 7 × 8 + 8 × 9 + 9 × 10 + 10 × 11 + 11 × 12

7×8+8×9+9×10+10×11+11×12
=7×10-2×7+8×10-8+9×10+10×10+10+11×10+11×2
=7×10-2×7+8×10-2×4+9×10+10×10+10+11×10+11×2
=10×（7+8+9+10+11）-2×7-2×4+10+11×2
=10×（7+8+9+10+11）-2×（7+4）+10+11×2
=10×（9×5）+10
=450+10
=460

If the centrosymmetric point of point P (m, 3-m) about the origin is in the second quadrant, then what is the value range of M?

The centrosymmetric point of point P (m, 3-m) about the origin is (- m, M-3)
Because it's in the second quadrant, so it's required
-m0
therefore
m>3