If a(a + 4) = 21 and b(b + 4) = 21, where a ≠ b, then a + b =
Select
A) −4
B) −5
C) 2
D) 46
E) 48
i.e. if a = 3 then b = -7   or if a = -7 then b = 3   But in each case a+b = -7+3 = -4   −4nswer: option −4
<result>A</result>
If a(a + 4) = 21 and b(b + 4) = 21, where a ≠ b, then a + b =