The domain of y = f (x) is [2,4], and the domain of y = f (logarithm of X with 2 as the base) is obtained

X in the two functions is different, so you can replace X in the second function with y, so you can get
Y = f (x) = f (logarithm of Y with base 2)
And X ∈ [2,4], the value range of bracket content should be the same, ㏒ 2, y ∈ [2,4], the solution is y ∈ [4,16]
So the domain of y = f (logarithm of X with base 2) is [4,16]

Which is the largest logarithm of LN π and log with base 2 and base 5

The spring scale is used to hang objects and submerge them in water. The indication of the spring scale is 1 / 3 of that of the object when it is weighed in air. The density of the object is ()
A. 0.3 × 103kg / M 3B. 0.67 × 103kg / M 3C. 1.5 × 103kg / M 3D. 3 × 103kg / M 3

∵ the object is immersed in water and still, and it is subjected to vertical upward buoyancy, tensile force and vertical downward gravity. Buoyancy, tensile force and gravity are equilibrium forces, ∵ f floating = g-13g = 23g = 23 ρ GV. According to Archimedes principle, f floating = ρ water GV, ∵ 23 ρ GV = ρ water GV, ∵ ρ = 32 ρ water = 1.5 × 103 & nbsp; kg / m3

Given the quadratic function y = 8x ^ 2 - (k-1) x + k-7, when the value of K is, the quadratic function takes the y-axis as the axis of symmetry? Write out its functional relationship

∵ quadratic function y = 8x ^ 2 - (k-1) x + k-7, with y axis as symmetry axis
∴-(k-1﹚=0
∴K=1
When k = 1, the quadratic function takes the Y axis as the symmetry axis
Its function formula is y = 8x & # 178; - 6

There are three cups of water, the mass of which is M1 = 10kg, M2 = 20kg, m3 = 30kg; the temperature of which is T1 = 80 ℃, T2 = 40 ℃, T3 = 20 ℃, respectively

m1t1+m2t2+m3t3=(m1+m2+m3)t
t=36.7℃

How to multiply negative numbers?
-3×-5=?
-5×-4=?

I don't know if you write this right. Do you want to add a small bracket to the negative number after the operation symbol? Negative is positive, and two negative numbers multiply or divide are positive; only one negative number and an integer multiply or divide, the result is negative

The horizontal track is connected with an arc-shaped smooth track with radius r = 2M and height h = 0.8m, as shown in the figure. An object from the horizontal track rushes to the arc track with initial velocity V0 and passes through the highest point without leaving the track. The range of initial velocity V0 of the object is calculated

Let the velocity of the object at the top be V, and the process from the horizontal orbit to the top of the circular orbit is obtained by the kinetic energy theorem. It is shown that - MGH = 12mv2-12mv02 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; if the object just reaches the top, that is v = 0, then it is obtained by Formula 1 that & nbsp; V0 = 2GH = 4m / s; Mg = mv2r, from which V2 = RG can be obtained. Substituting into Formula 1, we can get & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; V0 = 2GH + RG = 6m / S & nbsp; & nbsp; & nbsp; & nbsp; so the range of initial velocity v0 for an object to pass through the highest point without leaving the orbit is: 4 & nbsp; m / s < V0 ≤ 6 & nbsp; m / S & nbsp; & nbsp; answer: the range of initial velocity V0 for an object to pass through the highest point without leaving the orbit is 4 & nbsp; m / s < V0 ≤ 6 & nbsp; m / s

In the arithmetic sequence {an}, A3 = - 13, A9 = 11, find the maximum value of the first n terms and Sn

Solution: A3 = - 13, A9 = 11
So a1 + 2D = - 13
a1+8d=11
So A1 = - 21, d = 4
So an = - 21 + 4 (n-1) = 4n-25
So n ≥ 7, an > 0
n

If the car is accelerating uniformly along the straight road with an acceleration of 0.5m/s2, then ()
A. The final speed of the car must be equal to 0.5 times of the initial speed. B. the initial speed of the car must be 0.5 m / s higher than that in the first second. C. the final speed of the car must be 0.5 m / s higher than that in the first second. D. the final speed of the car must be 0.5 m / s higher than that in the first second

According to a = V − v0t, in any second: a. the final speed of the car is 0.5m/s larger or smaller than the initial speed, so a is wrong; B. the speed of the car at the beginning of this second is the same as that at the end of the previous second, so B is wrong; C. the final speed of the car is 1m / s larger than the initial speed in the previous 1s, so C is wrong; D. according to the formula, it can be seen that the steam

Xiao Gang is 2 years older than Xiao Liang, and Xiao Liang is 3 years older than Xiao Ming. The total age of the three is 35. How old are they

Let Xiaoliang be x years old, Xiaogang be x + 2 years old, Xiaoming be x-3 years old, the sum of the three ages is (x + 2) + (x-3) + x = 35, the solution is x = 12, Xiaoliang be 12 years old, Xiaogang be 14 years old, Xiaoming be 9 years old

The domain of y = f (x) is [2,4], and the domain of y = f (logarithm of X with 2 as the base) is obtained