Hello from MrBillDoesMath!
Answer:
(a+2)
Discussion:
Suppose
a^2 + 7a + 10 = (a+5) (a + b)
Then
a^2 + 7a + 10 = a^2 + (ab + 5a) + 5b => factor "a" from rhs, 2nd term
a^2 + 7a + 10 = a^2 + (b + 5)a + 5b
so 5b = 10 => b = 2
Hence
a^2 + 7a + 10 = (a+5) (a + 2)
Thank you,
MrB
