what is the units digit of ( 147 ^ 21 ) ^ 48 ?
the units digit of the exponents of 7 repeat in a cycle of four , which is { 7,9 , 3,1 } . the number 21 has the form 4 n + 1 so the units digit is 7 inside the bracket . the number 48 has the form 4 n , so the units digit is 1 . the answer is a .
add(add(const_4, const_3), const_2)