To silpify the expression we proceed as follows:
(x+7)/(x^2+4x-21)
Factorizing the given the denominator:
x^2+4x-21
x^2-3x+7x-21
=x(x-3)+7(x-3)
=(x-3)(x+7)
thus plugging back in our expression we have:
(x+7)/[(x-3)(x+7)]
simplifying this we obtain:
1/(x+3)
Answer: 1/(x+3)
