Given that an arithmetic sequence can be expressed as a linear function in the form f(x)=mx+b, write a linear function to describe the sequence {10,15,20,25,30,}

For this case we have:
 m = (y2-y1) / (x2-x1)
 m = (15-10) / (2-1)
 m = 5/1
 m = 5
 Then,
 y-yo = m (x-xo)
 where,
 (xo, yo) = (1, 10)
 Substituting:
 y-10 = 5 (x-1)
 y = 5x -5 + 10
 y = 5x + 5
 
 a linear function to describe the sequence is:
 y = 5x + 5