1. Find the solution set of inequality - x ≥ - 1. 2. Compare the size of 4 + 3A & # 178; - 2b + B & # 178; and 3a & # 178; - 2b + 1 by using "comparison size of difference method"

1. Find the solution set of inequality - x ≥ - 1. 2. Compare the size of 4 + 3A & # 178; - 2b + B & # 178; and 3a & # 178; - 2b + 1 by using "comparison size of difference method"

A:
1）
-x>=-1
Multiply both sides by - 1 to change sign:
x0
So:
4+3a²-2b+b²>3a²-2b+1

Calculation formula of resistivity of aluminum cable
Urgent: the output voltage is 380 V, the power is 40 kW motor, with copper cable transmission 1000 meters away, should use the area of aluminum wire?
My family bought 3 aluminum cables, each 16 square is enough?

The square of voltage divided by power equals resistance
Resistance = resistivity * length / area
Count it out

A group of numbers are arranged according to the law to form a sequence: 1, 3, 7, 21, 31 What is the 50th number in this sequence?

The following rules can be found: 1 = 1 × 1-03 = 2 × 2-1; 7 = 3 × 3-2; 13 = 4 × 4-3; 21 = 5 × 5-4; 31 = 6 × 6-5 So we can get the general term an = n ^ 2 - (n-1), so = (1 + 2 ^ + 3 ^ +...) +n^2)-(0+1+2+…… +(n-1))=n(n+1)(2n+1)/6-(n-1)n/2=n(n^2+2)/3S50=50(...

When the voltage at both ends of a conductor is 4V, the current intensity passing through it is 0.8A. When the voltage at both ends of a conductor is 6V, the current intensity passing through it is 0.8A______ A. Its resistance is______ Ω．

When the voltage at both ends of the conductor is 4V, the current is 0.8A, so the conductor resistance is r = UI = 4v0.8a = 5 Ω. When the voltage at both ends of the conductor becomes 6V, the conductor resistance is still 5 Ω, so the current passing through is I = ur = 6v5 Ω = 1.2A

What should be filled in 1 / 4 - 1 / 2Sin & # 178; 15 ° ()?

Original formula = 1 / 4 (1-2sin & # 178; 15)
=1/4*cos(2×15)
=1/4×cos30
=√3/8

Series circuit problems: a constant resistance, a sliding rheostat, voltmeter and ammeter, power supply and switch
The power supply voltage is 4.5V, the total current range measured by the ammeter is 0 ~ 0.6A, the resistance value of the constant value resistor is 5 ohm, the maximum resistance value of the sliding rheostat is 20 ohm, and the voltage range measured by the voltmeter at both ends of the sliding rheostat is 0 ~ 3V. In order to protect the two ammeters from damage, the resistance value range of the sliding rheostat is?

The maximum current is 0.6A, so the minimum total resistance is 4.5 / 0.6 = 7.5 Ω, so the minimum sliding rheostat is 7.5-5 = 2.5 Ω; the maximum voltage is 3V, then the voltage of constant resistance is 4.5-3 = 1.5V, the current is 1.5 / 5 = 0.3A, and the maximum sliding rheostat is 3 / 0.3 = 10 Ω

How to solve 27x + 4-3x-20 = 8x

8x moves to the left, 4 and 20 move to the right, that is: 27x-3x-8x = 20-4, the solution is: x = 1

There is a DC power supply with negligible internal resistance, which transmits current to two series resistors RA and Rb. When RA resistance is 90 Ω, short circuit will lead to power failure
No answers, I want algorithms

When the resistance of RA is 90 Ω, the current in the circuit after short circuit is 4 times of that before, then the resistance of Rb is 0_____
The current is four times the original, and the resistance is one fourth of the original
Rb / (Ra + Rb) = 1/4
The solution is RB = 30 Ω

Let f (x) be defined everywhere on R. it is proved that f (x) = [f (x)] ² / (1 + [f (x)] Λ4) is a bounded function on R

1、 When f (x) = 0, f (x) = 0, when f (x) ≠ 0, f (x) ＞ 0, ｜ f (x) ≥ 0, the function f (x) is bounded. 2. When f (x) ≠ 0, [f (x)] ^ 2 ＞ 0, ｜ [f (x)] ^ 2 ＋ 1 / [f (x)] ^ 2 ＞ 2, ｜ 1 / {[f (x)] ^ 2 ＋ 1 / [f (x)] ^ 2} ≤ 1 / 2

What should the total power of household appliances working at the same time not exceed that of the watt hour meter?

It should be
The total current of household appliances working at the same time should not exceed the current of energy meter