Need evaluate the expression 5x - 7 for x =9? what is the answer?

An expression involving a variable is a way to express an idea, rather than a specific number. So, writing means that there is a certain quantity, x, and you want to multiply it by 5, and then subtract 7.

Note that we don't want to know the value of x, we're only saying that we will multiply it by 5 and then subtract 7.

So, if we know that x=9, we will multiply it by 5 and then subtract 7:

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for