1.B 2..B. 3.D. 4。 D 5..6.B. 7.D. 8.C. 9.D. 10.A
fill (up) a vacancy
1.X = 6/5，Y =-7/52。 M = 0 n = 1 3。 X =110+3y/54.306 5.100 Yuan The value of 50 yuan 6.a is 65438. 9.-2/3 10.3
Third, answer questions.
( 1)x =-29/2y =-25/7(2)x = 1/3y =-3
2.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.
4. Solution:
At first, the master overhauled X meters every hour, and the apprentice overhauled Y meters every hour; Then later, the master overhauled 2x meters every hour.
Countable equation: 6x+6y = 2 10, 2 * (2x) = 6y;
Solution: x = 2 1, y = 14,
That is to say, at the beginning, the master overhauled 2 1 meter per hour and the apprentice overhauled 14 meter per hour.
5. Solution: Team A originally planned to repair X kilometers every day, while Team B originally planned to repair Y kilometers every day.
According to the original plan, it takes 50 days for Team A and Team B to cooperate.
In fact, the A * * * team has built it for 50 days, including X kilometers per day for 30 days and x+0.6 kilometers per day for 50-30 = 20 days.
Team b * * * repairs 50- 10 = 40 days, of which 30 days repair y kilometers every day, and the other 40-30 = 10 days repair y+0.4 kilometers every day;
Countable equation:
50(x+y) = 200，
30x+20(x+0.6)+30y+ 10(y+0.4)= 200；
Solution: x = 2.4, y = 1.6,
Namely: Team A originally planned to repair 2.4 kilometers per day, while Team B originally planned to repair 1.6 kilometers per day.
6. Because Xiaoying got the correct solution, she substituted the values of X and Y into the equations ax+by=9 and 3x-cy=-2.
The formula 2a+4b=9 (1) is obtained.
3*2-4*c=-2 (2) formula, here we get c= 2.
Then, because Xiao Liang copied C wrongly, he got x=4, y=- 1, so we can know that his solution still satisfies ax+by=9, because A and B are not copied correctly.
Bring his x and y into equation 4a-b=9 (3).
Therefore, a= 5/2 and b = 1 can be obtained from (1) and (3).
So a= 5/2, b= 1 and c= 2.