Change this radical to an algebraic expression with fractional exponents.5 sqr x^3

Anyone know these questions? i need ,.

Which statement is true about the extreme value of the given quadratic equation? a. the equation has a maximum value with a y-coordinate of -21. b. the equation has a maximum value with a y-coordinate of -27. c. the equation has a minimum value with a y-coordinate of -21. d. the equation has a minimum value with a y-coordinate of -27.

The half-life of iodine-131 is approximately 8 days. find the amount of iodine-131 left from a 42 gram sample after 16 days. a: 10.5 grams b: 21 grams c: 0.0006 grams d: 34 grams