Plz help urgent ,plz have step by step explanation find a and b

Identify which functions are linear or non-linear. a. f(x) = x2 + 1 b. f(x) = 2x + 5 c. f(x) = x 2 + 3 d. f(x) = 3 x + 7 e. f(x) = 4x + 10 2 - 5

Ahiker stands at an unknown elevation before he ascends 2 miles up a mountain to an elevation of 9 miles. find the elevation of the hiker before his ascent.

For the following equations, find the ratio of a to b. be sure to show all of your work. a. 3a = 6b b. 15a = 5b