If a of B equals C of D (BD is not equal to 0), then a minus a of B equals C minus C of D. please explain the reason

If a of B equals C of D (BD is not equal to 0), then a minus a of B equals C minus C of D. please explain the reason

a/a-b=1-a/b,c/c-d=1-c/d,
Because a / b = C / D,
So 1-A / b = 1-C / D,
So a / A-B = C / c-d
Do you understand? I hope you can adopt it

Given that a and B are opposite numbers, C and D are reciprocal, and a ≠ 0, what is the value of 3A + 3B + Ba CD?

Because a and B are opposite to each other, a + B = 0, Ba = - 1. Because C and D are reciprocal to each other, CD = 1. So 3A + 3B + Ba CD = 3 (a + b) + Ba CD = 3 × 0 + (- 1) - 1 = - 2

There are five Mondays in June, but only four Tuesdays. What day is April 1 of that year?

June has 30 days, and June 30 is Monday. Because there are 91 days from April 1 to June 30, April 1 is Tuesday

(1) Divide the data into four groups and draw the frequency distribution histogram. The ratio of height of each small rectangle is 1:3:4:2. If the frequency of the second group is 15, then the sample size is 1:3:4:2______ .
(2) There are 40 data in a group, which are divided into six groups. The frequency of group 1-4 is 10,5,7,6 respectively. If the frequency of group 5 is 0.10, then the frequency of group 6 is 0______ .

15÷3/（1+3+4+2）=50
2、40-10-5-7-6=12
12-40×0.1=8
8÷40=0.2

21 × 11 = 231, 12 × 11 = 132. What's the rule?

A two digit number * 11 is equal to ten, which is written in the hundred, and ten + one is put in the middle

On junior high school mathematics, the problem of quadratic equation with one variable
We know the equation about X: the square of X - 2mx + the square of quarter * n = 0, where m and N are the lengths of the waist and bottom of an isosceles triangle
1. Proof: this equation has two unequal real roots
2. If two roots X1 and X2 of the equation satisfy | x1-x2 | = 8 and the area of isosceles triangle is 4, find the value of M and n
Please help, I want this problem is very urgent, thank you!

Because m, n is the length of the waist and the bottom of an isosceles triangle, the equation has two unequal real roots. 2. According to the relation between heel and coefficient, the two roots x1, X2 satisfy | x1-x2 | = 8

3.5.13.13 how can these four numbers be equal to 24?

3-5+13+13

A few years later, students get together, 30 good friends, every 2 good friends shake hands once, how many times do you need to shake hands?

The arrangement and combination is very simple, 30 * 29 / 2 = 435 times

Simple calculation of 98 × 27 + 54

98×27+54
=（100-2）27+54
=100×27-2×27+54
=2700-54+54
=2700

How to solve the equation x + 4x = 13!

x+4x=13
（1+4）x=13
5x=13
x=13÷5
x=2.6