Ask all kinds of math masters to give you a solution, give a formula, thank you!

Let the interest rate be a and the principal amount be n. The interest per day is the principal multiplied by the interest rate = na. This question 4000=7x15000xa——a=

If it is a rolling interest, then the interest on the first day is na, and the principal becomes n+na=n(1+a), and the interest on the second day is n(1+a)a, and the principal becomes n(1+a)+n(1+a)a=n(1+a)*(1+a)=n(1+a) 2

The principal appreciates at 154,000 after 7 days

154000=150000（1+a）^7

1+a)^7=154000/150000=a=

The second question is that the principal is 43,400, and the interest is 16,000, 10 days.

According to the first algorithm a = 16000 10 43400 = according to the second algorithm, the principal appreciation on day 0 is 59400

59400=434001(1+a)^10

1+a)^10=59400/43400=

Simple interest: 4000 (7*150000) = 1,000th of the daily interest rate.

16000 (10*43400) = 1000th of the daily interest rate.

10 times worse alas!

Solution: f(x-12)=f[(x-6)-6]=-f(x-6)=f(x) function is a periodic function with a period of 12.

f(x)=f(2-x)

Replace x with 1-x to obtain: f(1-x)=f[2-(1-x)]=f(1+x) function to the axisymmetric function with x=1 as the axis of symmetry.

f(a)=-f(2016)=-f(12×168+0)=-f(0)=-f(6-6)=f(6)

f(x) is monotonic on [5,9], and only one function value is f(6)a=6 on the interval [5,9].

Scratching through the middle, it is clear that the red triangle is an equilateral triangle.

The length of the green line = 3 r + r

3r is the length of the green line in an equilateral triangle.

r is the radius of the circle.

As the bottom total length is 90The green line is 45

So there is 45 = 3r + r

Therefore r = 45 (1 + 3).

13.-2 or 414 a

16.Remember to adopt it, thank you!

1) Encounter problem (two people walk in the opposite direction, face to face) Suppose that A and B start from points A and B at the same time, walk in opposite directions, and meet at point C, the velocity of A is v1, and the velocity of B is v2; When they walked H hours and repented of each other, then the distance they walked was S A and S B.

Encounter distance = speed and * encounter time.

s A + s B) = v A*h + v B * h

s A + s B) = (v A + v B) * H

Then: The sum of the distances traveled by A and B is the distance they met.

The time of the encounter is the same, both h

2) Chase the problem (the two of them go in the same direction).

Suppose that A and B start from point A and B at the same time, and the two of them are traveling in the same direction (point A is far away from point C) and meet at point C, the velocity of A is v1, and the velocity of B is v2; They walked for h hours and met in the spring.

Chase distance, speed difference, chase time.

s A-s B) = v1*h + v2*h

s A-s B) = (v1-v2)*h

Then: the distance to be pursued is: the distance taken by A - the distance traveled by B.