Write the equation of a line that passes through (1,9) and has a slope of -3, please!

y = -3x + 12

Step-by-step explanation:

Very similar to the other question i answered, by here's a step by step anyway in case you find it helpful : )

There are lots of different methods to do these types of questions, but this is the way i like to do it.

Coordinate (x1, y1) : (1, 9) and Gradient (m): -3

Start with this generic equation:

y- y1 = m(x-x1)

Substitute in the values they have given you:

y - (9) = -3(x-1)

This becomes:

y -9 = -3x +3

Keep solving by moving the 10 over to the other side:

y = -3x + 3 +9

y = -3x + 12

An easy way to double check:

1) the coefficient of x is the slope. We got -3x, and the slope is -3, so that's correct.

2) Substitute x=1 into the equation, and we get 9, which is the exact coordinate that they gave us. This is also right.

Hope this helped : )

c

step-by-step explanation:

agree

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