Question

Find the common difference for the sequence shown.

56, 49, 42, 35, ...


-12
-7
7

Answer 1

-7

Answer 2

What is the method for finding common difference?

Answer 3

The difference is 7. You cant have a difference of a negative number.

Answer 4

56 - 49 = ?

49 - 42 = ?

42 - 35 = ?

The difference is found when you subtract the first number from the one coming after it.

Answer 5

yes the difference is 7 but you have to use a negative to subtract otherwise you would be adding.

Answer 6

Common difference is not first number - second number. It is second number - first number. It can be positive or negative, which denotes whether the sequence is increasing or decreasing. The common difference is 49 - 56 = -7

Answer 7

Ahh, my bad.

Answer 8

$$\tt a_1+(n-1)d=a_n\text{ for n=1,2,... and d>0. }\\\text{Here d = 7}. $$

Answer 9

@ybarrap If you put 7 for d in your equation you will get a sequence different from the one in the question. d can be negative as well.

Answer 10

You are right! d = -7, sorry about that.
$$a_1=56\\
a_2=56+(2-1)*(-7)=56-7=49\\
a_3=56+(3-1)*(-7)=56-14=42\\
etc. $$