In solving the equation (x + 3)(x + 1) = 48, Eric stated that the solution would be
x + 3 = 48 = x = 45
or
(x + 1) = 48 = x = 47
However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.

Question

In solving the equation (x + 3)(x + 1) = 48, Eric stated that the solution would be
x + 3 = 48 => x = 45
or
(x + 1) = 48 => x = 47
However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.

anonymous · Answer

the solution fails because 48 is composite number 
it rhs would have been a prime then their is a chance of getting the sol.
it is better to simplify and use the factorisation of trinomials r Sridhacharyas method to obtain the rrots of the quadratic eq.
then one might get the roots as 5,-9