Find (x,y) to get square numbers

Find all ordered pairs (x, y) such that x and y are integers and

(1) 1^x + 9^y is a perfect square

(2) 2^x + 8^y ...............................

(3) 3^x + 7^y ................................

(4) 4^x + 6^y ...............................

(5) 5^x + 5^y ...............................