According to your data, if the clock had started at the 0-second mark then what would be the reading at each of the marks?

You've learned to do the algebra.  Now we're learning to use the functions.

Excel classifies linear, logarithmic, polynomial, power and exponential functions.

Linear functions are of the form y = mx + b.

Power functions are functions like y = x^2, y = c^3, y = x^-5, y = x^.5, y = x^-.4.

Polynomial functions are sums of positive-integer power functions, like y = 5 x^3 - 7 x^2 + 3x - 9.

Quadratic functions are degree-2 polynomials with y = a x^2 = b x + c.

Exponential functions raise some base to a power, e.g., y  = 2^x, or y = .5^x, or y = e^x.

y vs. x means ...