Please give the junior 3 sisters a little bit of knowledge points for the junior 2!

1. (1) Bring x=1 into the equation to obtain: 1-(2m+1)+m2+m=0, that is, m2-m=0 is solved to get m=1 or m=0

2) When m=1, the original equation is x2-3x+2=0, i.e., (x-2)(x-1)=0 is solved to obtain x=1 or x=2

When m=0, the original equation is x2-x=0 and the solution is x=1 or x=02, and the percentage of price reduction is x, then after two price reductions** from 100 yuan to 100 (1-x) (1-x).

100 (1-x) (1-x) = 81

1-x）2= 1-x=

Solution x = A: .

You may want to set the number of junctions to x

Then the total number of people is: 4x+78, because 8x is not enough points, then there are: 4=<8x-(4x+78)<8

Solution: 20<=x<21, rounded, x=20Total number of people: 4 * 20 + 78 = 158

It is equivalent to putting the remaining 78 people and 4 people to each intersection, and the last one is a few people less.

So the number of intersections = 78 4 rounded = 20.

Number of people = 20 * 4 + 78 = 158 people.

It's a very simple question.

There are x intersections, and if there are 8 people at each intersection, then there are y people at the last intersection (4 "Y<8)".

4x+78=8(x-1)+y

86-y=4x

Since the number of people can only be an integer, y can only take four numbers: 4, 5, 6, and 7.

In the same way, intersection x can only be taken as an integer.

As long as you bring them in one by one and take a look, you can find that y=6, x=20 is the only answer, so there are 20 intersections, 158 people.

By the way, the upstairs is strong, I am incompetent in mathematics, from childhood to adulthood is just the basic idea, the kind of jumping around and jumping out of the answer, worship it

This profit margin is the profit divided by the cost, so let's assume that the cost of ABC's three products is ABC. For merchant A, let's say that the sales volume of A is X, so the sales volume of B and C are both X 2. Then the equation can be listed as:

Finishing can obtain b=2a+2c

For merchant B, if the sales volume of B is Y, then the sales volume of A is Y 2, and the sales volume of C is 4Y 13. Then B's profit margin is:

Substituting b=2a+2c, the profit margin is 56%, the process is a bit complicated, but it is a basic operation.

Solution: Let the growth rate be x 500 desks produced in January The output will be reduced by 10% in February, and the production of desks will be 500 * (1-10%) = 450 450 * (1+x) (1 + x) = 648 450 + 900x + 450x 2-648 = 0 450x 2 + 900x-198 = 0 x 2 + 2x-198 450 = 0 x 2 + 2x-044 = 0 x=(-2+24) 2 or x=(-2-24) 2 for help from the root finding formula Ask a question from the second year of junior high school and be very grateful

This junior high school doesn't require the first formula.

a (has + past participle, apparently only a is the past participle form).

b (he asked for a cup of coffee and a plate of dumplings, apparently here b).

A (translation: I have no water in my cup, can you give me some?) From this, we can choose a).