How do i know if a relation is a function on a graph ?I don’t quite understand the explanation on the pic.

Arianna is buying plants for her garden. she buys 15 flowering plants for $96. pink flowering plants sell for $8, and purple flowering plants sell for $5. how many pink flowering plants did arianna buy? i figured out the answer! the answer is 7. 8x +5y = 96 plug in 7 for x 8 (7) + 5y = 96 56 + 5y = 96 subtract 56 from both sides 5y/y = 40/5 y = 8 she bought 7 pink and 8 purple plants

Find the zeros of each function. f(x) = x^2 + 5x - 6

Use sigma notation to represent the following series for 9 terms.