Answer:
Step-by-step explanation:
This is arithmetic sequence so you should go to linear equations in your head.
Think of the question asking you to find the equation of line going through the points:
(14,-33) and (15,9).
First, let's find the slope.
You need to compute y's change over x's change.
The way I like to do that is line up the points vertically, subtract them, and then put 2nd difference over first.
Like this:
( 15 , 9)
-( 14 , -33)
------------------
1 42
So the slope is 42/1=42.
(The slope is our common difference.)
Now point slope form is:
y-y1=m(x-x1) where m is the slope and (x1,y1) is a point you know on the line.
So we have m=42 and (x1,y1)=(15,9). (You could have chose the other point.)
y-9=42(x-15)
I'm going to put in slope-intercept form. Slope-intercept form is y=mx+b where m is the slope and b is the y-intercept.
y-9=42(x-15)
Solve for y by adding 9 on both sides:
y=42(x-15)+9
Distribute 42 to terms in the ( ) :
y=42x-42(15)+9
y=42x-630+9
y=42x-621
So we can which back to n now: