Junior 1 math problems, math 1 questions

1.It takes x days for B to be done alone. i.e. do 1x per day

30/x+20(1/40+1/x)=1

1/2+50/x=1

50/x=1/2

x=1002.According to the title, it can be obtained:

x/40+y/100=1

5x+2y=200

i.e. y=(200-5x) 2 70

12＜x＜15

When x=13.

y=not a positive integer, rounded).

When x=14.

y=65 is in line with the topic.

A:

1. Let A complete x every day and B complete y every day.

40x = 30y+20(x+y)

20x=50y

y = so the time required for B is 40 days.

2. Let A do day A and day B do day B.

ax+by = 40x

Because y=so2b+5a = 200

If b=70, then a=12, since b<70, so a>12, and a<15, so a can only be 13 or 14, when a is 13, b is not a positive integer, so a can only be 14, b is 65, A did 14 days, B did 65 days.

Replace a with -b, and c with 1 d. Equal to 3

From the meaning of the title: b = a and cd = 1 b is not equal to 2 3 = >a is not equal to (-2 3) i.e. 3a + 2 is not equal to 0

3a-6b+6）/（2cd+3a）= 9a+6)/(2+3a)

3(3a+2)/(3a+2)

A one-dimensional equation is one with only one unknown, and the highest unknown is once, so m=1

2x+5=0

Neither is the solution.

Solution: 2x-1=0

Shift, get: 2x=1

Merge similar items to obtain:

x=1 2 coefficients into one, get:

x=I got this answer because there is a law: move an item to change the sign.

The sign refers to a number or symbol in front of an equation, such as: +, x, .

That is, positive and negative numbers.

When a positive number shifts, it becomes a negative number, and vice versa.

So x=let's check it again:

Bring x= to the equation:

2x-1=0

is equal to: Method 1:

Suppose his family's actual water consumption in September is xm

Xiao Ming's family paid a total of 20 yuan in water bills in September, so it must have been exceeded.

If the water consumption does not exceed 10m, the charge is yuanm, and the excess part is yuanm.

Then: 10* +x-10)*1=20

Solution: x=25(m).

Let the actual water consumption be x

10*x=25 cubic meters.

Solution: The school has 2x fans and 3x computers.

2x+3x=90

5x=90x=18

18 2 = 36 units.

18 3 = 54 units.

A: The school has 36 fans and 54 computers.

Untie; Set the team to win x games and draw (11-x) games, according to the title, get.

3x+1(11-x)=23

solution, x=6

A:The team has won a total of 6 games.

Let x be the number of wins and y be the number of draws.

3x+y=23

x+y=11

Solution: x=6, y=5

Let x be the number of wins and y be the number of draws.

3x+y=23

x+y=11

Solution: x=6, y=5

1. 3x=15-2x

3x+2x=15 (shift, according to the property of equation 1)2 -5x=4

x=-4 5 (coefficient is 1, according to the property of equation 2).

Shifting Equation Fundamental Properties 1

Shifts Fundamental properties of the equation 2

Solution: 4

A: It takes 12 minutes for the correspondent to catch up with the student queue.

10 minutes, it's a question about the speed difference. It is calculated that the distance traveled by the student in half an hour is 2 km, and the speed difference between the correspondent and the student is 12 km/h. The distance traveled by the student divided by the speed difference is the time it takes for the correspondent to catch up with the student.