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Seven math high score plans, one volume from chapter 7 to the end of chapter 2.
Chapter VIII

First, multiple-choice questions 1. B

2..B.

3.D

4.D

5..A.

6.B。

7.D。

8.C。

9.D。

10. Fill in the blanks

1.x=6/5,

y=-7/5

2.m=0

n= 1

3.x= 1/ 10+3y/5

4.30

six

5. 100 yuan

50 yuan

6. The value of a is 18.

7. This two-digit number is 23.

8.3 children, 1 1 pear.

9.

-2/3

10.3 III. Solving problems (1)x=-29/2

y=-25/7

(2)x= 1/3

y=-32.k=4

3. Because X and Y are solutions of four equations, X = 1 can be solved from 5x+y=3 and x-2y=5, Y =-2 can be brought into AX+5Y = 4 and A- 10 = 4, so a= 14 can be brought into 5x.

x

Meters, apprentice maintenance once an hour.

y

Rice; Later, the master overhauled it every hour.

2x

rice. Countable equation: 6x+6y

=

2 10

, 2 *(2 times)

=

6y

; Solution: x

=

2 1

,y

=

14

At first, the master overhauled it every hour.

2 1

Meters, apprentice maintenance once an hour.

14

rice. 5. Solution: Team A originally planned daily maintenance.

x

Km, team b originally planned to repair it every day.

y

According to the original plan, Team A and Team B need to cooperate.

50

Day; In fact, Team A was repaired.

50

Day, in which

30

Repair every day.

x

Kilometers, in addition

50-30

=

20

Repair every day.

x+0.6

Km, team B * * * has been repaired.

50- 10

=

40

Day, in which

30

Repair every day.

y

Kilometers, in addition

40-30

=

10

Repair every day.

y+0.4

Kilometer; Countable equation: 50(x+y)

=

200

,30x+20(x+0.6)+30y+ 10(y+0.4)

=

200

; Solution: x

=

2.4

,y

=

1.6

Team a was going to repair it every day.

2.4

Km, team b originally planned to repair it every day.

1.6

Kilometers 6. Because Xiaoying got the correct solution, she substituted the values of X and Y into the equation.

ax+by=9

And 3x-cy=-2: 2a+4b=9.

Formula (1)

3*2-4*c=-2

Type (2)

The conclusion here is that

c=

Then, because

Xiao Liang copied C wrong.

X=4,y=- 1。

You can know because A and B didn't copy correctly.

So his solution still satisfies ax+by=9.

Bring his x, y into

get

4a-b=9

(3) So

Pass (1) and (3)

work out

a=

5/2,

b=

1, so

a=

5/2,

b=

1

c=

2