250=50k+b
100=200k+b
Solution:
k=- 1
b=300
The functional relationship between y and x is y =-x+300;
(2)∵y =-x+300;
When x= 120, y = 180.
The purchase price of brand A is RMB A, and the purchase price of brand B is RMB 2a.
120a+ 180×2a=7200,
Solution: a= 15,
B brand unit price 30 yuan.
Answer: The unit purchase price of two brands of stationery boxes is 15 yuan, 30 yuan;
(3) If brand A buys M, then brand B buys (-m+300).
15m+30(-m+300)≤6300
4m+9(-m+300)≥ 1795
Solution: 180≤m≤ 18 1,
∵m is an integer,
∴m= 180, 18 1.
* * There are two purchase schemes:
Scheme 1: A brand procurement 180, b brand procurement120;
Scheme 2: A brand purchase 18 1, B brand purchase119;
The profit from selling all the two brands of pencil cases is W yuan.
W=4m+9(-m+300)=-5m+2700。
∫k =-5 < 0,
∴W decreases with the increase of m,
∴m= 180, w max = 1800 yuan.
I hope the landlord will adopt it. Thank you.