When k is equal to, y = kx-x is a linear function?

When k is equal to, y = kx-x is a linear function?

y=(k-1)x
So k-1 ≠ 0
k≠1

When 0 ≤ x ≤ 2, the corresponding function value y is 2 ≤ y ≤ 4, then the value of K + B is 0

① When k > 0, the function is incremental
So when x = 0, 0 + B = 2, B = 2
When x = 2, 2K + 2 = 4, k = 1;
So K + B = 2 + 1 = 3
② When k

Given the first-order function y = KX + B, and 2 less than or equal to x less than or equal to 6, 5 less than or equal to y less than or equal to 9, find the analytic expression of the function

In two cases, when k is greater than 0, it is an increasing function, then x = 2, y = 5, x = 6, y = 9, k = 1, B = 3
If K is less than 0, then x = 2, y = 9, x = 6, y = 5, k = - 1, B = 11
The analytic formula is y = x + 3 or y = - x + 11