Which expression is represented by the diagram?

6 negative tiles. 1 tile is crossed out.
Negative 6 minus (negative 1)
Negative 6 minus 1
Negative 5 minus (negative 1)
Negative 5 minus 1

To find the inverse of a number a, one can use the equation f(c) = a-1/c=0 where c is the inverse of a use the secant method of finding roots of equations to find the inverse of a = 2.5 ,er = 0.001%