Question

Which ordered pair is the solution to the system of equations?

http://static.k12.com/bank_packages/files/media/mathml_b1373eed21bba09d8452cb84aa9cee0825d5d67e_1.gif

A.
(3, 4)

B.
(5, 3)

C.
(7, 2)

D.
(15, 7)

Answer 1

you have a choice
a) you can solve the system and what the answer is or
b) substitute each ordered pair in the system and see which one is correct
first method is probably easiest here given your choices

Answer 2

\[2x-5y=-5\\
x+2y=11\]

Answer 3

yea i want to go with choice A

Answer 4

multiply the second equation all the way across by \(-2\)

Answer 5

what do you get?

Answer 6

so i would multiply -2 by 2?

Answer 7

sorry i am so confused

Answer 8

yes, everything in the second equation
all terms

Answer 9

\[-2(x+2y)=-2\times 11\] multiply it all

Answer 10

-2*2=-4 correct?

Answer 11

yes

Answer 12

-2*11=-22

Answer 13

yes

Answer 14

so i would have -2x +-4y=-22? correct?

Answer 15

yes or just
\[-2x-4y=-22\]

Answer 16

oh ok

Answer 17

now the system looks like
\[2x-5y=-5\\
-2x-4y=-22\] now add them in a column

Answer 18

the x terms go bye bye which was the whole point of multiplying by \(-2\)

Answer 19

ok

Answer 20

i'm still kinda confused though

Answer 21

me too, i am always confused
what do you get when you add?

Answer 22

idk i still don't get it

Answer 23

do you know what i mean by "add"?

Answer 24

no because the eqauation you gave me is subtraction

Answer 25

\[2x-5y=-5\\
-2x-4y=-22\]___________
your answer here

Answer 26

i know what the word add means

Answer 27

\(2x+-2x=?\)

Answer 28

0

Answer 29

2x + -2x=0

Answer 30

got it !
\(-5y+-4y=?\)

Answer 31

-5y+-4y=-9

Answer 32

close, it is \(-9y\)

Answer 33

and finally what is \(-5+-22\)?

Answer 34

oh because i have to add all the 'y'

Answer 35

-5+-22=-27

Answer 36

ok so now we have
\[-9y=-27\]

Answer 37

solve this for \(y\) in one step

Answer 38

i have to divide and i get 3

Answer 39

wait what?!

Answer 40

i get what your saying

Answer 41

then you are done

Answer 42

but i have to find which pair goes with the equation

Answer 43

only one answer choice has \(y=3\)
normally you would also solve for x by substitution, but you don't need to in this case

Answer 44

doesn't 'y' come second?

Answer 45

yes it sure does, just like it does in the alphabet

Answer 46

so my answer is B. Coorect?

Answer 47

must be, it is the only one with \(y=3\)

Answer 48

thx here is a medal for helping me

Answer 49

: )

Answer 50

thank you we might meet again bye