Question

function 1
graph of a curve
○ linear
○ not linear
function 2
graph of a line (with a break?)
○ linear
○ not linear
function 3
graph of a curve
function 4
graph of a wave-like curve

Explanation:

Step1: Analyze Function 1

A linear function has a straight - line graph (constant slope). Function 1's graph is a curve (exponential - like), so it's not linear. Mark "Not linear".

Step2: Analyze Function 2

Function 2's graph is a straight line (even with a break, the visible part has constant slope), so it's linear. Mark "Linear".

Step3: Analyze Function 3

Function 3's graph is a curve (polynomial with degree > 1, has peaks and valleys), so it's not linear. Mark "Not linear".

Step4: Analyze Function 4

Function 4's graph is a curve (periodic, sinusoidal - like), so it's not linear. Mark "Not linear".

Answer:

Function 1: Not linear; Function 2: Linear; Function 3: Not linear; Function 4: Not linear