K= {(2, 1), (3, 2), (4, 1), (5, 3)} is k-1 a function and why?

If your question regards K⁻¹, the inverse of the function K, then the answer is, ...

... No. K⁻¹ is not a function.

The range of K is {1, 2, 1, 3} which includes 1 twice. This would be the domain of the inverse relation. A relation that has repeated values in its domain is not a function.

5x+40

5(x + 8)

7x - 49

7(x - 7)

18x + 9

9(2x + 1)

15x - 10

5(3x - 2)

step-by-step explanation:

for number one all you have to do is factor 5 out of 5x + 40

for number 2 factor 7 out of 7x - 49

for number three factor 9 out of 18x + 9

for number four factor 5 out of 15x - 10

i belive those are the ones that are under 90 degreese.