LGA = LGB why is a not necessarily equal to B? It's not what the teacher said. A > 0 b > 0 is a = B. I can't understand it. They are senior teachers in Tianjin No.1 middle school with many years of teaching experience

LGA = LGB why is a not necessarily equal to B? It's not what the teacher said. A > 0 b > 0 is a = B. I can't understand it. They are senior teachers in Tianjin No.1 middle school with many years of teaching experience

If we say LGA or LGB, then a and B must be positive. There is no need to emphasize this. For example, when we say 1 / x, X must not be zero, otherwise it is meaningless. Similarly, if a and B are not positive, then the logarithmic formula is meaningless

If LGA = 2.431, LGB = 1.431, then B / A is equal to

lgb-lga=lgb/a=-1,b/a=1/10

Why can LGA + LGB = 2 be derived from a + B = 2

Can't launch
We can take a = 1, B = 1
Then a + B = 2
LGA + LGB = 0 + 0 = 0 is not equal to 2

1 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9?

1+[1+2+3+...+(n-1)]
=1+n(n-1)/2

After a 3V 1.5W small bulb L is connected in series with a 12 Ω resistor, the small bulb will light up normally

(1) R lamp = U2 / P = 3V × 3V / 1.5W = 6 Ω
(2) The bulb lights normally, so I = P / u = 1.5w/3v = 0.5A
U resistance = IR resistance = 0.5A × 12 Ω = 6V
U = u Lamp + U resistance = 3V + 6V = 9V

The third grade calculation question (| 36-m ^ 2 | + 8 (m-2n) ^ 2) / under the root sign (M-4) = 0, find the value of M + n
(| 36-m ^ 2 | + 8 (m-2n) ^ 2) / under the root sign (M-4) = 0, find the value of M + n
The absolute value of (M-4) parts (36 minus the square of M) under the root sign plus the square of 8 times (m-2n)
How to calculate? Why is n ^ - M + 9 obviously wrong?

∵ the number of square root (i.e. M-4) must be greater than 0
And ∵ (| 36-m ^ 2 | + 8 (m-2n) ^ 2) / under the root sign (M-4) = 0
∴|36-m^2|+8(m-2n)^2=0
∵ absolute value is greater than or equal to 0, square is greater than or equal to 0
That is | 36-m ^ 2 | ≥ 0
8(m-2n)^2≥0
And ∵ 36-m ^ 2 | + 8 (m-2n) ^ 2 = 0
∴|36-m^2|=0
8(m-2n)^2=0
∴m^2=36 ,m-2n=0
∴m=±6
∴n=±3
∴m+n=±9
I am also junior three, very hard to do ah

When a resistor is applied with a voltage of 10V at both ends, the current passing through it is 0.5A, then the resistance value of the resistor is Ω. If the voltage at both ends of the resistor is zero, the resistor is Ω
The resistance is Ω

10/0.5=20 Ω
The voltage across the resistor is zero, and the resistor is still 20 ohm

In the parabola y2 = - 8x, the linear equation of the chord with (- 1,1) as the midpoint is ()
A. x-4y-3=0B. x+4y+3=0C. 4x+y-3=0D. 4x+y+3=0

The chord is not perpendicular to the x-axis, so let the point (- 1,1) be the parabola of the midpoint, and the two ends of the chord y2 = - 8x be a (x1, Y1) B (X2, Y2) to get yi2 = - 8X1, Y22 = - 8x2. Subtracting the two formulas to get (Y1 + Y2) (y1-y2) = - 8 (x1-x2) ∫ Y1 + y2 = 2 ∧ k = - 4 ∧ the linear equation is y + 1 = - 4 (x-1), that is 4x + y + 3 = 0, so choose: D

If the resistance of a copper wire is r, the invalid measure is ()
A. stretch the copper wire and connect it into the circuit
B increase the voltage at both ends of the wire
C will fold the copper wire into the circuit
D reduces the current through the wire

Answer: BCD
Analysis: BD will not change its resistance, a is larger, C becomes a quarter of the original

Find the value of X in the following formulas: (1) x & # 178; = 25; (2) (x-1) &# 178; = 9; (3) x & # 179; = - 64

  x^2=25x=±5(x-1)^2=9x-1=±3x1=3+1=4,  x2=3-1=2x^3=-64x=-4