Let's clarify what you are doing, and then find your error (which is pretty simple) rather than find a different way to do it.

You forgot to use parentheses to show the

order of operations, which makes your work very hard to follow; also, you used "x" for the multiplication symbol, which is not a good idea in algebra where x is usually a variable. I'll use "*", which is standard in typing. So here is what I think you meant:

(y-4)/(-2-(-4)) * (-2-(-1))/(-1-4) = -1 .

From this I get: (y-4)/2 * -1/-5= -1.

From this I get: 10 * (y-4)/2 * 10 * 1/5 = -1.

The first two lines are correct; you are finding the slopes of the lines, and writing an

equation that says their product is -1.

The next line is wrong. You seem to be multiplying each of the factors on the left by 10, and not changing the right side! I suppose your idea is to use the LCD; but that is not needed for a product (only for a

**sum**), and when you use it, you have to make sure you multiply the entire value on each side by the

**same thing**.

In effect, by multiplying

**twice **on the left by 10, you have multiplied by 100, so you should be multiplying the right by 100 also.

I would not do that; I would just multiply the fractions on the left together, and then multiply both sides by the new

denominator.

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