Question

if a=4 ,a5= -20 find d​

Answer 1

a4 = 4

a + 3d = 4 ---> 1

a5 = -20

a + 4d = -20 ---> 2

From 1 and 2

a + 3d = 4

a + 4d = -20

- - +

__________

- d = 24

d = -24