## Migitmack 3 years ago One endpoint of a segment is (12,-8). The midpoint is (3,18). Find the coordinates of the other endpoint.

1. CliffSedge

Could use the formula, but it's easy enough to just reason through it: What number is the same distance from 3 as 12, and what number is the same distance from 18 as -8?

2. Migitmack

Can U just tell me I am kinda lazy -_-

3. CliffSedge

Nope. Stop being lazy. I will draw a picture for you though.

4. CliffSedge

|dw:1346614090275:dw|

5. CliffSedge

Your other option is to use the formula: $M(x,y)=\left(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2}\right).$

6. Migitmack

1 sec

7. cathyangs

@Migitmack , @CliffSedge is explaining it quite well. Openstudy is supposed to help you study, it's not an answer-generator.

8. Migitmack

Whats M

9. CliffSedge

M=midpoint.

10. Migitmack

I don't understand

11. Migitmack

i did the formula

12. Migitmack

but I where is the M

13. CliffSedge

You have the coordinates for the midpoint and one other point, so rearrange the formula to solve for what you don't know. (If you want to use the formula.. I still think just doing some elementary subtraction is more straight-forward) |dw:1346614542836:dw|

14. Migitmack

I hoy (7.5, -72)?!!!!!?! I think I did something wrong

15. CliffSedge

Just look at the first picture I drew and ask yourself these questions: 1. 3 is halfway between 12 and what other number? That's your x. 2. 18 is halfway between -8 and what other number? That's your y.

16. Migitmack

Is X 9 or 7?

17. CliffSedge

The formula would look like this: $M(3,18)=(\frac{12+x}{2},\frac{-8+y}{2}).$ Handle the x and y equations separately: $3=\frac{12+x}{2}, \space 18=\frac{-8+y}{2}$

18. CliffSedge

The distance from 3 to 12 is 9, so what number is also 9 units away from 3, but in the other direction? Use the same reasoning for y.

19. Migitmack

For Y its going to be 5?

20. Migitmack

@CliffSedge

21. Migitmack

@Cliffsedge yo is it 5 for y?

22. CliffSedge

Why do you think 5 for y? How did you get that number?

23. CliffSedge

I'm guessing you're finding the midpoint of (3,18) and (12,-8) but (3,18) *is* the midpoint.