How to solve {80 / (x + y) + 42 / (X-Y) = 7, 40 / (x + y) + 70 / (X-Y) = 7 (⊙ o ⊙) {80 / (x + y) + 42 / (X-Y) = 7 40 / (x + y) + 70 / (X-Y) = 7

How to solve {80 / (x + y) + 42 / (X-Y) = 7, 40 / (x + y) + 70 / (X-Y) = 7 (⊙ o ⊙) {80 / (x + y) + 42 / (X-Y) = 7 40 / (x + y) + 70 / (X-Y) = 7

The idea of this problem is very simple, that is, a system of binary equations. First of all, divide the left term of the two equations respectively, the denominator (X & # 178; - Y & # 178;) and the right term (7) of the two equations are the same, then their molecules are also equal, that is, 122x-38y = 110x + 30y

Solve the following system of linear equations: {x + y = 42 and 0.8% x + 1.1% y = 42 × 1%

x=14,y=28

How much is 1 + 1

It's a matter of reasoning. You have one apple, and others give you one apple. Of course, there are two

Material composition:
Confucius had a student who saw a child fall into a fast river and jumped down to rescue him. The child's father gave him a cow to express his gratitude, and he accepted it happily. Everyone talked about it and thought that he was too greedy. Confucius said to him, you are right, because your behavior declares to the society: as long as you save people at risk, no matter how big the reward is, you can accept it, This can encourage more people to save people
In the spring and Autumn period, the government of the state of Lu had a rule that when people of the state of Lu traveled abroad, if they saw that they had become slaves abroad, they could pay money to redeem them first, and then go to the government to repay them after returning home. A student of Confucius redeemed people but did not repay them. People praised him for his noble character. Confucius severely criticized him, saying that his behavior prevented more slaves from being redeemed, Because if people advance money to redeem slaves, they will suffer losses if they don't repay them, but if they repay them, their character is not as good as that of Confucius' students, so they have to pretend not to see them
It's better to write a composition instead of thinking

Given a = - 2009, B = 2010, C = - 2011, try to find the value of a ^ 2 + B ^ 2 + C ^ 2 + AB + BC AC

a²+b²+c²+ab+bc-ac
=(2a²+2b²+2c²+2ab+2bc-2ac)/2
=[(a+b)²+(b+c)²+(a-c)²]/2
=(1+1+4)/2
=3

Given that P is a function y = 2 / x, and the distance from P to the origin is 2, then the coordinates of the qualified point P are obtained______ .

The answers are as follows:
Let the coordinates of point p be: (a, 2 / a)
√[（a-0）^2+(2/a-0)^2=2
a^2+4/a^2=4
a^4-4a^2+4=0
(a^2-2)=0
a^2=2
So: a = √ 2 or a = - √ 2;
So the coordinates of point P are: (√ 2, √ 2) or (- √ 2, √ 2)

X + 1 / 3 = 9 / 10 solution

That is, x = 9 / 10-1 / 3 = 27 / 30-10 / 30 = 17 / 30

Given vector group A1, A2, A3, linearly independent, prove: vector group A1 + A2, A2 + a3, A3 + A1, linearly independent

Suppose that a1 + A2, A2 + a3, A3 + A1 are linearly correlated
a3＋a1=m(a1＋a2)＋n(a2＋a3)
(m－1)a1＋(m＋n)a2＋(n－1)a3=0
Since A1, A2 and A3 are linearly independent, then:
M-1 = 0 and M + n = 0 and N-1 = 0
But this system of equations has no solution
A1 + A2, A2 + a3, A3 + A1 are linearly independent

Whose second power is 1024?

The answer is 32

Given that the sum of the first n times of the arithmetic sequence {an} is Sn, and S2 = 10, S5 = 55, then the coordinates of the direction vector of the line passing through P (n, an) and Q (n + 2, an + 2) (n ∈ - n *) can be______ ．

The sum of the first n terms of ∵ arithmetic sequence {an} is Sn, and S2 = 10, S5 = 55, ∵ a1 + A2 = 10, A3 = 11, ∵ A1 = 3, d = 4, ∵ an = 4n-1an + 2 = 4N + 7, ∵ P (n, 4N-1), q (n + 2, 4N + 7) ∵ the slope of line PQ is 4N + 7 − 4N + 1n + 2 − n = 4, ∵ P (n, an) and Q (n + 2, an + 2) (n