A and B are vertical angles. If A = 4x - 10 and B = 6x - 30, find mA.

- anonymous

A and B are vertical angles. If A = 4x - 10 and B = 6x - 30, find mA.

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- Nnesha

pic ??

- Nnesha

vertical angles are equal

- anonymous

There is no picture.

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## More answers

- Nnesha

alright so a and b are vertical angles
vertical angles share the same vertex
|dw:1434116295080:dw|
for example here ^^^ a = b c=d
a and are vertical angles and c and d are vertical equal so they are equal to each other
\[\huge\rm 4x-10=6x-30\]
solve for x

- anonymous

So when I solve 4x-10 i get 2.5 and when i solve 6x-30 i get 5.

- Nnesha

wait what ? how did you get 2.5
and why did you solve it separately ?

- anonymous

I divided 10 by 4 & i got 2.5

- Nnesha

no no no!
4x MINUS 10 you can't divide by 10

- Nnesha

write all x value to the one side of equal sign
and constant term to the other side
*constant term (number without variable )

- Nnesha

\[\huge\rm 4x-10=6x-30\]
subtract 4x both sides

- anonymous

There is a theorem that states two vertical angles are congruent, i.e. have the same angle measure.
Thus A = B. Substituting in the values we have for A and B you get a linear equation that can be solved to find x.
4x - 10 = 6x - 30
-10 = 2x - 30
20 = 2x
10 = x
Now that we know x, substitute back into the expression for A.
A = 4x - 10 = 4*10 - 10 = 40 - 10 = 30
mA = 30

- anonymous

Thank you.

- Nnesha

remember to cancel out
addition === >opposite subtraction
multiplication ===> opposite division

- Nnesha

so to cancel 4x from left side you should subtract 4x both sides :-)

- Nnesha

|dw:1434117089054:dw|
let me know what you get

- anonymous

x=20

- Nnesha

how did you get 20 please show your work so i can find your mistake :-)

- anonymous

|dw:1434117408586:dw|

- anonymous

|dw:1434117516941:dw|

- Nnesha

alright thanks!
and combine like terms are add or subtract coefficient of SAME varaible
6x-30 <--- you can't subtract because 6 have x and 30 doesn't have x |dw:1434117600094:dw|
there is NEGATIVE 30 at right side how would you move that to the left side ???

- Nnesha

add or subtract 30 both sides ?

- anonymous

add.

- Nnesha

yep add 30 both sides |dw:1434117716411:dw|
still... we have to isolate x
so how would you cancel out 2 from the right side ?? :-)

- anonymous

|dw:1434117733194:dw|

- Nnesha

yep yep divide! you got it!!
so x = ??

- anonymous

x=10

- Nnesha

yep now be careful
x=10 but they want us to find A
so substitute x value in this equation
\[\large\rm A =4x-10\]

- anonymous

so the answer is A=10? lol i dont know

- Nnesha

nope x=10 you need mA
so replace x by 10
A=4x-10 and then solve for A

- Nnesha

\[\huge\rm A=4\color{green}{x}-10\]
plug in 10

- anonymous

|dw:1434118220477:dw|

- Nnesha

:-)yaya!

- anonymous

i get it!

- Nnesha

yeah :-)gO_Od job!

- anonymous

Lol thank you.

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