If you subtract a number from 7 / 15 of the numerator, and add the denominator to the number, you can divide it into 1 / 10

If you subtract a number from 7 / 15 of the numerator, and add the denominator to the number, you can divide it into 1 / 10

Let x 10 (7-x) = 15 + x 11, x = 55, x = 5

What is the difference of 7 out of 8 minus 5 out of 6 divided by 1 out of 24

Seven out of eight minus five out of six divided by one in 24
=(21/24-20/24)÷1/24
=1/24÷1/24
=1

The energy meter of Xiaoming's household appliance is marked with the word "1200R / kW · H". When only the TV set is working in his home, the TV set will be consumed if the turntable rotates 120 times in 50 minutes______ &The power of TV is______ W．

∵ consume 1kW · h of electric energy, the electric energy meter turns to 1200, the electric energy meter turns to 120, the consumption of electric energy: w = 1200kW · H = 0.1kw · h, the power of TV: P = wt = 0.1kw · h5060h = 0.12kw = 120W

The factorization result of the polynomial 2xy-x & # 178; - y + 1 & # 178; is
A（x-y+1）(y-x+1) B (x+y-1)(y-x+1) C(x+y-1)(x-y+1) D(x-y+1)(x-y--1)

2xy-x²-y+1²
=-(x-y)²+1
=（1+x-y）（1-x+y）
So choose a
Have a good time

If the mass ratio of metal to oxygen is 9:8, what is the relative atomic mass of the metal? 20.4g the mass of oxygen contained in the oxide is equivalent to the mass of oxygen contained in G Fe3O4?

+The molecular formula of the oxide of 3-valent metal element is: x2o3. Suppose the atomic weight of the metal is m, then: (2 × m) / (3 × 16) = 9 / 8, and the solution is m = 27. So the metal element is al (aluminum), and the relative atomic weight is 27. The mass fraction of oxygen in Al2O3 is 8 / (9 + 8) = 8 / 17, and the mass fraction of oxygen in Fe3O4 is 0

The formula of 1 + 2 + 3 + 4 +. + 121 =

Let Sn = 1 + 2 + 3 + 4 +. + n
Then Sn = n + (n-1) + (n-2) + (n-3) +. + 1
Then the two equations are added left and right to get 2Sn = (n + 1) + (n + 1) + (n + 1) + (n + 1). (n + 1) = (n + 1) * n
Then Sn = (n + 1) * n / 2
Substituting n = 121
We can get Sn = 7381

The electromotive force of the power supply is 3V, the internal resistance is 0.2 Ω, and the external circuit resistance is 1.8 Ω

Current I = 3 / 2 = 1.5A, terminal voltage U = 1.8 * 1.5 = 2.7V, electric work w = i2rt

To find the limit of (n & # 178; + 2) ^ 1 / 6 - (n-1) ^ 1 / 3, please give the process

R is equal to 10 ohm, the power supply voltage remains unchanged, and a 30 ohm resistor is connected in series. The current is 0.25 a
How to connect a resistor in the circuit to make I2 = 1.25A?
What's the resistance R2?

If R is equal to 10 ohm and a 30 ohm resistor is connected in series, the total resistance is r = 10 Ω + 30 Ω = 40 Ω
Power supply voltage U = i1r total = 0.25A * 40 Ω = 10V
To make I2 = 1.25A, a 10 Ω resistor R2 needs to be paralleled in the circuit, because the current passing through R2 is U / r2 = 10V / 10 Ω = 1a
Plus the original 0.25A, it's 1.25A

If the abscissa of the midpoint of the line AB is equal to 2, the length of the chord [AB] can be obtained

Let (kx-2) & sup2; = 8xk & sup2; X & sup2; - (4K + 8) x + 4 = 0, let a (a, b), B (m, n), then a + M = (4K + 8) / K & sup2; = 4K + 2 = k & sup2; k = - 1 or K = 2K = - 1, △ = 0, there is only one intersection, so k = 2, a + M = 4, am = 1 | ab | & sup2; = (a + m) & sup2; - 4am = 12 | ab | = 2