First of all thanks for the great book:)
I have a question regarding page 156 question 4:
Why is only 1 the right answer and not also 3?
Glad you’re enjoying the book! 1 and 3 are both x-values where the parabolas intersect, but the question asks for the least possible value of a. 3 would be the answer if the question asked for the greatest possible value of a.