It is known that m and N are constants. If the solution set of MX + n > 0 is x < 13, then the solution set of nx-m < 0 is () A. x＞3B. x＜3C. x＞-3D. x＜-3

It is known that m and N are constants. If the solution set of MX + n > 0 is x < 13, then the solution set of nx-m < 0 is () A. x＞3B. x＜3C. x＞-3D. x＜-3

The solution set of MX + n ＞ 0 is x ＜ 13, the direction of unequal sign changes, and 〈 m ＜ 0 and - nm = 13, 〈 nm = - 13 ＜ 0, ∵ m ＜ 0. 〉 n ＞ 0; from nx-m ＜ 0, X ＜ Mn = - 3, so x ＜ - 3; so D

It is known that the solutions of the equations {MX + 2ny = 4, x + y = 1. {X-Y = 3, NX + (m-1) y = 3 are the same. Find the value of (1) the same solution (2) m, n
Sit down. Come on

(1) Methods: the data were collected from the patients
x+y=1
x-y=3
The solution is x = 2, y = - 1
(2) Substitute the other two
2m-2n=4
2n-(m-1)=3
The solution is m = 6, n = 4

If the equations MX + 2ny = 4, x + y = 1 and X-Y = 3, NX - (m-1) y = 3 have the same solution
(1) Find the same solution
(2) Finding the solution of M, n

According to the problem equations MX + 2ny = 4, x + y = 1 and X-Y = 3, NX - (m-1) y = 3 have the same solution, we can list a system of equations x + y = 1, X-Y = 3. Find out its value x = 2, y = - 1. Then bring x, y into the other two equations, list another system of equations 2m-2n = 4, 2n - (- 1) (m-1) = 3, and calculate M = 8 / 3
n=2/3

How to prevent the 110V power supply equipment from burning the switch power supply when it is inserted into the power supply higher than 220V by mistake? What are the good measures to prevent the switch power supply from being damaged
The switching power supply itself has the switch to adjust 110V and 220V, that is to say, it was inadvertently inserted into the 220V that day, and the high voltage burned this switching power supply? How can we avoid human misoperation?

This kind of thing happens from time to time. The simple and sure way to protect is: connect a 130v varistor in parallel behind the fuse of 110V power supply equipment. As long as the input voltage is greater than 130v, the varistor will be reduced and the fuse will be burnt out, thus protecting the equipment

The circumference of the bottom circle of a cylindrical oil barrel is 24m, and the height is 6m. A gecko crawls from a place 1m away from the bottom to diagonally B to hunt for food. The shortest route of its crawling is as follows
How long is it?

Shortest route = √ (6-1) &# 178; + 24 & # 178; = √ 601 M

When only this consumer works in the circuit, the measured energy consumption is 0.3 kW · h within 15 min. this consumer may be
When a certain electrical appliance works normally, the electric energy consumed within 15 minutes is 0.3 kW · h, and the electrical appliance may be
A. Air conditioner B. refrigerator
C. Television D. radio
In fact, I want to know how to find out the air conditioner

15 minutes is a quarter of an hour. Isn't it 1.2 kilowatt hour that one hour consumes?
1.2kW is 1200W, only air conditioner can have such high power... Ordinary oven has such large energy, power is only more than 800W, hope to adopt!

1-4+9-16+… +(- 1) n + 1n2 equals ()
A. n(n+1)2B. -n(n+1)2C. （-1）n+1n(n+1)2D. （-1）nn(n+1)2

Resistance: how many Ω is 1K

1K means 1000, which has nothing to do with Ω
1K Ω equals 1000 Ω

1-2 + 3 + 4-5 + 6 + 7-8 + 9 + 10-11 + 12 +... 97-98 + 99

1-2 + 3 + 4-5 + 6 + 7-8 + 9 + 10-11 + 12 +.. + 97-98 + 99. From the formula, the first and the last are 100, the second and the penultimate are 100, but they are negative; the third and the penultimate are 100, and the fourth and the penultimate are 100. Basically, the formula can be divided into three groups, and the calculation result is 100, so it can be divided into 33 groups, and the result should be 33 100, that is 3300

How to understand the acceleration effect of resistor and capacitor in series circuit with LED lamp after a resistor and a capacitor are connected in parallel
If the problem is a simple logic pen circuit in part (the main part is a 555 timer), a resistor and a capacitor in parallel, how can play the role of acceleration?

If there is no capacitor in this circuit, the LED will light up after power on. There is a process from dark to bright, which takes a long time