if a ( a + 4 ) = 21 and b ( b + 4 ) = 21 , where a ≠ b , then a + b =
"i . e . if a = 3 then b = - 7 or if a = - 7 then b = 3 but in each case a + b = - 7 + 3 = - 4 answer : option a"
add(divide(21, const_10), divide(21, divide(21, const_10)))