help solve by substitution?

Question

x+3y=-15
-9y=3x+45
answers
A) -3,-4
B) -3,4
C)many solutions
D)no solution

Answer 1

ok

x + 3y = -15
-9y = 3x + 45

if you rearrange equation 2 its the same as equation 1 multiplied by -3

-3x - 9y = 45

Since you have 2 variables with just 1 equation you cant get an answer
hence no solution

Guessing can give you 2 possible solutions
-3, -4
or
3 and -6
or
6 and -7
or
9 and -8
and so on to give many answers

Answer 2

Solve the first equation for x:
x = -15 - 3y

Plug that into x in the second equation:
-9y = 3(-15 - 3y) + 45

Distribute the 3:
-9y = -45 - 9y + 45

Combine like values:
you'll find that both equal 0

d) no solution

Answer 3

x + 3y = 15
x = 15 - 3y

***
-9y = 3x + 45
-9y = 3(15-3y) + 45
-9y = 45 - 9y + 45
-9y = 90 -9y
0 = 90
False stmt - no solution

Answer 4

Since both for instance (-3,-4) and (0,-5) are solutions to BOTH equations the correct answer is that there are infinite solutions, not "No Solution".

D)

Answer 5

C) many solutions

If you multiply the first equation by 3 on both sides, you get the second equation. Therefore, there are multiple solutions.

Answer 6

line them up the same...one on top of the other!


x + 3y = -15
3x + 9y = -45

4x+12y=-60

now sub #'s for x and y from the given....x=-3 and y=-4 works! just sub in the answers given to see if they work! or....just try each set in both of the given equations..if it works in both...then it is right!

Answer 7

-3 + 3(-4) = -15
-3 + (-12) = -15
-15 = -15

-9(-4) = 3(-3) + 45
36 = (-9) + 45
36 = 36
Answer is A

Answer 8

c i guess thats how i always did but its no joke ya this thing is cheap on ask ?s