It is proved that the necessary and insufficient condition for an image of a linear function y = - M / NX + 1 / N to pass through the first, second and fourth quadrants at the same time is Mn 〉 0 It is proved that the necessary and insufficient condition for an image of a linear function y = - M / NX + 1 / N to pass through the first, second and fourth quadrants at the same time is Mn 〉 0

It is proved that the necessary and insufficient condition for an image of a linear function y = - M / NX + 1 / N to pass through the first, second and fourth quadrants at the same time is Mn 〉 0 It is proved that the necessary and insufficient condition for an image of a linear function y = - M / NX + 1 / N to pass through the first, second and fourth quadrants at the same time is Mn 〉 0

To pass through quadrants 1, 2 and 4, there must be - M / N0
That is Mn > 0, and N > 0
That is, M > 0, n > 0
So if and only if M > 0 and N > 0
Mn > 0 is only a necessary and insufficient condition (because it also contains M)

The image of the first-order function y = KX + B passes through one, three and four quadrants, and the intersection points of x-axis and y-axis are a (m, 0) B (0, n) known: M + n = - 3, Mn = - 10
Analytic expressions of two functions
Come on, t, t

The solution m + n = - 3 Mn = - 10 N1 = = 2 N2 = - 5 M1 = - 5 M2 = 2
A1 (- 5,0) A2 (2,0) B1 (0,2) B2 (0, - 5)
The image of linear function y = KX + B passes through one, three and four quadrants, that is, x > 0, y

It is known that the intersection of a parabola and x-axis is a (- 1,0), B (m, 0) and passes through the point C (1,n) of the fourth quadrant, and M + n = - 1, Mn = - 12. The analytical formula of this parabola is obtained

∵ point C (1, n) is in the fourth quadrant ∵ n < 0. From M + n = - 1, Mn = - 12, we can get m = 3, n = - 4. Let the analytic formula of parabola be y = AX2 + BX + C. substituting points (- 1.0), (3, 0), (1, - 4), we can get the solution of a − B + C = 09A + 3B + C = 0A + B + C = - 4, a = 1, B = - 2, C = - 3, so the analytic formula of parabola is y = x2-2x-3