Answer:
(x +5)(x +6)
Explanation:
You're looking for two factors of 30 that total 11.
30 = 1×30 = 2×15 = 3×10 = 5×6
5+6 = 11, so those are the numbers you want in the binomial factors.
x^2 +11x +30 = (x +5)(x +6)
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Additional comment
You will notice that ...
(x +a)(x +b) = x^2 +(a+b)x +ab
The constant is the product of the factor constants, and the x-coefficient is their sum.