Exponential Functions: Find the equation through the points A and B in the form y = a b x

Question 1:

A is (0,2) and
B is (1,4)
y = 2 × 2 x

Question 2:

A is (0,-5) and
B is (1,-10)
y = -5 × 2 x

Question 3:

A is (0,4) and
B is (2,16)
y = 4 × 2 x

Question 4:

A is (1,15) and
B is (5,1215)
y = 5 × 3 x

Question 5:

A is (1,-15) and
B is (5,-1215)
y = -5 × 3 x

Question 6:

A is (3,40) and
B is (4,80)
y = 5 × 2 x