(2) Total profit = profit of a kind of apple+profit of b kind of apple+profit of c kind of dried radish. Then according to the relationship between Y and X obtained in (1), the functional relationship between W and X is obtained, and then according to the range of independent variables and the nature of functional relationship, the most profitable scheme is obtained.
Solution: (1) From the meaning of the question:
2.2x+2. 1y+2(20-x-y)=42
Simplification: y=20-2x? (3 points)
∵? x≥2？ 20-2x≥2，
The value range of ∴x is: 2 ≤ x ≤ 9.
(2) From the meaning of the problem:
w = 6×2.2x+8×2. 1(-2x+20)+5×2x
=- 10.4x+336，
∫k =- 10.4 < 0, and 2≤x≤9.
When x=2, w has a maximum.
W max =-10.4× 2+336 = 315.2 (hundred yuan)
∴ A: 2 vehicles; B: 16 vehicles; C: Two cars.
2. Analysis: (1) function image can be used to judge that these points are on a straight line, that is, on the image of a linear function;
(2) let y=kx+b, substitute two coordinates, and solve with equations;
(3) Let y in the analytical formula obtained in (2) be equal to 44, and then find x. 。
Solution: (1) As shown in the figure, these points are on the image of a linear function;
(2) let y=kx+b,
From the meaning of the question? 22= 16k+b？ 28= 19k+b，
Solve? k=2？ b=- 10，
∴ y = 2x- 10。 (x is some discontinuous values. Generally speaking, x is 16, 16.5, 17.5, 26, 26.5, 27, etc. );
(3) When y = 44, x = 27.
Answer: The length of this person's shoes is 27 cm. ..
I hope it helps you!