Answer:
Only the first and fourth cases are straight lines.
Step-by-step explanation:
If the x values have a constant increase (1,2,3,4... etc), a straight line will also have constant intervals in the y-values (4,6,8,10...).
To identify straight lines if the x-values have constant intervals, just check if y-values have also constant (but may be different intervals.
Case (from left to right)
1.
x = 4,5,6,7 (difference: constant = +1)
y = 7,8.75, 10.5, 12.25 (constant difference = 1.75, so straight line.
2.
x = 21, 22, 23, 24 (difference: constant = +1)
y = 98, 75, 56, 37 (differences are 23, 19, 19, so NOT a straight line)
3.
x = -12, -11, -10, -9 (difference : constant = +1)
y = 4, -1, -4, -7 (differences are -5, -3, -3) so NOT a straight
4.
x = 40, 41, 42, 43 (difference : constant = +1)
y = -18, -22.5, -27, -31.5 (differences are -4.5, -4.5, -4.5, so constant, straight line.
