Ask 3 math questions, ask 3 math questions, and I m sorry to trouble everyone

5 (hours) A: After 5 hours, the two cars met.

4 (hours) A: After the encounter, the bus will have to travel for 4 hours to reach place B.

1.20% of number A is equal to 25% of number B, and 20% of number B is equal to 25% of number C. Which of the three numbers A, B, and C is the largest? （a ）

a.A number bNumber B.

c.C number 2In a sugar water with a sugar content of 2% you are especially? After grams of sugar and 100 grams of water, what is the sugar content of sugar water? （ c）

b.Higher than 2%.

c.Less than 2%.

3.The highway between A and B is 450 kilometers long, and a passenger car and a truck drive out of the two places at the same time, and travel opposite each other, and the passenger car runs from A to B for 50 kilometers per hour; Trucks travel 40 kilometres per hour from B to A. Q:

After a few hours of two cars meeting? (The answer is 5 hours) How many hours will the bus have to travel to get to place B after the encounter? (columnar).

450 divided by 50 5

How do you know if you got it right? bc

Let x50+40)x=450A:

The existing urban population and rural population of this city are x,y people x+y=42 respectively

x(1+1%)+y(1+

2.The cost of the two garments is X and Y yuan.

x+y=500

x divided by 50% times 90% + y divided by 40% times 90% = 500 + 1573According to the above information, list the monthly payment fee y and the relationship time x time of the Internet time; y=

x is an arbitrary value.

Monthly subscription: y=50x+

x is 1 to 12

of any positive integer 2

It can be known from the question. b=a-7 simplification yields ab-50 and brings in the result of 1-7 51

2.Didn't make it.

3.I don't know if it's right. Reduced to.

b≤√b. b=0.Half of the establishment.

b＜0.To make it valid. b is an imaginary number, which does not match the value of b 1Not true.

0 b 1, half established.

In summary. When 0 b

A+B A+B was established.

2. The property of the convex function: f(a)+f(b)>=2f((a+b) 2), which is twice the value of the function at the midpoint.

If the numerator is less than or equal to the sum of the endpoint function values, the numerator of the limit expression of the problem is taken a=x+h, b=x--h, so the numerator is greater than or equal to 0, so the limit is greater than or equal to 0. And the limit is f''(x), hence f''(x)>=0。

3. When x is not equal to 0, g'(x)=(xf'(x)--f(x)) x 2 is obviously continuous. So just think about it.

g'(x) Continuity at 0. g'(0)=lim (g(x)--g(0))/x=lim f(x)/x^2=lim f'(x)/(2x)=f''(0)/2。

g'(x) is continuous at x = 0, i.e., lim g'(x)=g'(0) Established.

Because lim g'(x)=lim (xf'(x)--f(x))/x^2=lim xf''(x)/(2x)=lim f''(x)/2=f''(0)/2=g'(0)。

The above limits are all based on Robida's law. Therefore, the conclusion is valid.

4. Lobida's law is sufficient.

lim f(x)=lim f(x)*lnx/lnx =lim (f(x)/x+f'(x)*lnx)/(1/x)

lim f(x)+xlnx*f‘(x)=l

You'd better glue the questions on.