Question

the midpoint of AB is (3,-5) A =(9,4) What are the coordinates for B.

I know there is a trick to figuring this out by adding/subtracting the individual coordinates by each other. Any help?

Answer 1

@galacticwavesXX

Answer 2

ok you know the midpoint formula is \[M=(\frac{ x1+x2 }{ 2 },\frac{ y1+y2 }{ 2 })\]

Answer 3

\[M=AB=(3,-5)\]
Mx=3 & My=-5
so,
\[Mx=\frac{ x1+x2 }{ 2 }, My=\frac{ y1+y2 }{ 2 }\]

Answer 4

you understand what i've done so far?

Answer 5

Yes you separated the midpoint coordinates for x and y

Answer 6

yup now we know what x1 & y1 are and also what Mx & My is.
Now all we have to do is plug them in to the designated equation and solve for x2 & y2

Answer 7

Tell me what you get for x2 & y2 when you're finished solving for the problem

Answer 8

Im lost I got -5=(9+y2)/2 for My

Answer 9

no it should be \[My=-5=\frac{ 4+y2 }{ 2 }\]

you are solving for y2, so you know you have to set the equation to y2

Answer 10

x1=9 & y1=4. They should only be used in their respective formulas.

Answer 11

Still confused sorry

Answer 12

\[Mx=\frac{ x1+x2 }{ 2 }\rightarrow3=\frac{ 9+x2 }{ 2 }\]

set everything to x2 so the equation will be,
\[(3*2)=9+x2\rightarrow6=9+x2\rightarrow-3=x2\]

you can now see x2= -3

\[My=\frac{ y1+y2 }{ 2 }\rightarrow-5=\frac{ 4+y2 }{ 2 }\]
solved for y2, the same way you solved for x2.

\[(-5*2)=4+y2\rightarrow-10=4+y2\rightarrow-6=y2\]

you can see that y2 = -6

so, \[B=(-3,-6)\]

Answer 13

\[M=(Mx,My)=AB\] just to help

Answer 14

woahhhhhhhhh it should be B=(-3,-14)

Answer 15

lol arithmetic error

Answer 16

Yea I saw, -5-9=13

Answer 17

-13* Thanks

Answer 18

lol -5-9=-14 but yea sign always gets me, most irritating mistake to make in math