(i) 4x2 - 3x + 7
It's a polynomial in one variable i.e., x
(ii) y2 +
It's a polynomial in one variable i.e., y
(iii) + = 3t1/2 + t
It is not a polynomial as degree of t is not a whole number.
(iv) y + = y + 2y-1
It is in not a polynomial as degree cannot be negative (-ve) in polynomial.
(v) x10 + y3 + t50
It is polynomial but not in one variable as variables are x, y and t here. Hence, it is a polynomial in three variables.