Could you explain please the fraction as exponent, also negative exponent? I am a little bit confused.

With a fractional exponent, the numerator of the fraction indicates a power (a whole-number exponent), and the denominator of the exponent indicates a root. For example, 5 with the fractional exponent 3/4 indicates cubing the 5 and then finding the fourth root of that number. You could also first find the fourth root of 5 and then cube that number. Either way you get the same result: 3.3437. A negative exponent indicates a reciprocal. For example, 5 to the power of -2 indicates the reciprocal of 5². 5² is 25, whose reciprocal is 1/25.