So the resolution function is y=2x+4.
2. Simultaneous y=4-3x and y=2x- 1, and the solutions are: x= 1, y= 1, so the intersection point is (1, 1).
And y=ax+7 passes through the intersection of linear functions y=4-3x and y=2x- 1,
So 1=a+7,
So a=-6
3. Let the proportional function be y=kx and the proportional resolution function be y=4/3x, because it passes through point (3,4).
Let the linear function be y=kx+b, that is, the intersection with the y axis is b.
S=3*b/2= 15/2 (it should be the absolute value of b, which is difficult to express).
So b=5 or -5.
And because the function passes through points (3, 4),
So k=3, b=-5 or k=- 1/3, b=5.
That is, the main resolution function is y=3x-5 or y=- 1/3x+5.