What is the simple method of 173 * 73-73 * 73

What is the simple method of 173 * 73-73 * 73

173*73-73*73
=(173-73)*73
=100*73
=7300

(2/3)+(5/9)+(8/27)+(11/81)+(14/243)+...+[(3n-1)/(3^n)]
Find the value of the formula,

Let Sn = 2 / 3 + 5 / 9 + 8 / 27 + 11 / 81 + 14 / 243 +... + (3n-1) / (3 ^ n) ∧ 1 / 3Sn = 2 / 9 + 5 / 27 + 8 / 81 + 11 / 243 +... + (3n-4) / (3 ^ n) + (3n-1) / 3 ^ (n + 1) ∧ sn-1 / 3Sn = 2 / 3 + 3 / 9 + 3 / 27 + 3 / 81 +. + 3 / 3 ^ n - (3n-1) / 3 ^ (n + 1) + [1 / 3 + 1 / 9 + 1 / 27 +...]

A polynomial a subtracts the quadratic power of the polynomial 3x + 6x-7. Xiao Ming copied the minus sign into the plus sign, and the result of the operation is the quadratic power of - 2x + 3x-9. Do you know that
What is the correct result

（ ）+3X2+6X-7=-2X2+3X-9
Namely
（ ）=-2X2+3X-9-3X2-6X+7
=-5X2-3X-2
Results: the power of - 5x is - 3x-2

Simple algorithm of 600-197

600-197
=600-(200-3)
=600-200+3
=400+3
=403

Given the differential equation (x + 1) f "(x) + (x + 2) f '(x) = 0, find f' (x)

e^x(x+1)f''(x)+e^x(x+2)f'(x)=0
(e^x(x+1)f'(x))'=0
e^x(x+1)f'(x)=C
f'(x)=Ce^(-x)/(x+1)

The inequality ax − 3x + 1 ≤ 1a (where a ＞ 0 and a ≠ 1) about X is solved

When a ＞ 1, there is x − 3x + 1 ≤ − 1, that is, X − 3x + 2 ≤ 0, ∪ x2 + 2x − 3x ≤ 0, that is, (x + 3) (x − 1) x ≤ 0, ∪ x ≤ - 3 or 0 ＜ x ≤ 1. When 0 ＜ a ＜ 1, there is x − 3x + 1 ＞ − 1, ∪ - 3 ≤ x ＜ 0 or X ≥ 1

18 divided by 25 columns vertical

On the problem of limit in higher number one: when x tends to zero, what is the limit of (xsin1 / x + 1 / xsinx)?
The answer in the book is 0. I think it's 1. I'd like to know which expert can help me answer it!

It's 1, that's right. The former tends to 0 and the latter tends to 1

In the bivariate linear equation 4x + 3Y = 7, if x and y are opposite to each other, then X=____ y=_____

Y = - x
Substituting into the equation 4x + 3Y = 7
We get 4x-3x = 7
The solution is x = 7
y=-7
In the bivariate linear equation 4x + 3Y = 7, if x and y are opposite to each other, then X=_ 7_ y=_ -7_

Find the sum of 1 + 12 + 123 + 1234 + 12345 + 123456 + 1234567 + 12345678 + 123456789

137147205