To write the equation, we need the slope and y-intercept.
Remember that slope is the same as rate of change
or the change in y over the change in x.
Start by setting up a table with x and y values
which I have provided below.
Filling out our table, our given points are (10, 50) and (25, 20).
In the y column, we can see that the value of y
goes from 50 to 20 so it decreases by -30.
This means that the change in y is -30.
In the x column, we can see that the value of x goes from 10 to 25
so it increases by 15 which means that the change in x is 15.
So the rate of change is -30/15 which simplifies to -2.
To find b, we can use any ordered pair
in our table as the values for x and y.
Let's use the first ordered pair.
So we have 50 = -2(10) + b.
Solving from here, we get 50 = -20 + b.
Now add 20 to both sides to get 70 = b.
So if our slope is -2 and our y-intercept is 70,
we can substitute these values into our formula.
This gives us y = -2x + 70.