Question

For the following system, if you isolated y in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

4x − y = 8
2x + 3y = 9

A 8 – 4x
B 8 + 4x
C –8 + 4x
D –8 − 4x

Answer 1

Solve for y in the first equation

y=4x-8

Answer 2

4x - y = 8
-y = 8 - 4x
y = 4x - 8

Answer 3

So it would be A

Answer 4

More like C

Answer 5

no...it is -8 + 4x

Answer 6

ohhhhhh okay i understand now :)

Answer 7

that is good that you understand :)

Answer 8

thanks for all your help :)

Answer 9

I was not the only one that helped....but your welcome for the part I did :)

Answer 10

@incomplte thanks for your help ;)

Answer 11

You guys are so nice lol. We are just here to help

Answer 12

could you guys help me with some more?

Answer 13

what ya got ?

Answer 14

If you wanted to eliminate the y variable by adding the two equations in the following system, what could be your first step?

2x − 4y = 6
3x − y = 12

A Add the two equations together
B Multiply the first equation by –4
C Multiply the second equation by –4
D Multiply the second equation by 4

Answer 15

multiply 2nd equation by -4.....C

Answer 16

thanks @texaschic101 :)

Answer 17

@texaschic101 could you help me with just 2 more?

Answer 18

lets have them....

Answer 19

The three Math Idol judges have been eliminating contestants all day! The number of one-step equations and two-step equations who have been eliminated today is equal to 840! If three times the number of one-step equations minus twice the number of two-step equations is equal to 870, how many one-step equations auditioned today?

A 330
B 510
C 520
D 660

Answer 20

a stands for one step equations
b stands for two step equations

a + b = 840 ---> a = 840 - b
3a - b = 870

now sub 840 - b in for a in the second equation.....

do u know how to do this with the information I have given u ?

Answer 21

to get the answer i would have to subtract 840-870? is that right

Answer 22

wait i got 510 is that correcT?

Answer 23

no.....let me show you....
I set the 2nd equation up wrong....
It is supposed to be 3a - 2b = 870 (sub 840 - b in for a)
3(840 - b) - 2b = 870
2520 - 3b - 2b = 870
2520 - 5b = 870
2520 - 870 = 5b
1650 = 5b
1650/5 = 5b/5
330 = b

a + b = 840
a + 330 = 840
a = 840 - 330
a = 510

check...
3a - 2b = 870
3(510) - 2(330) = 870
1530 - 660 = 870
870 = 870 (correct)

yes you have it right......sorry I told you wrong about the equation....you must have found my mistake to get the correct answer....good for you.