Give the solution set to the system: y = 9 – 2x and 2x – 5y = 15.?

Question

Also:

Which numbers cannot be used in place of x in the rational expression?

-13/1-2x

Answer 1

2x + y = 9
2x - 5y = 15

Subtract the 2nd equation from the 1st.

6y = -6
y = -1

Substitute for y in 1st equation.

2x - 1 = 9
2x = 10
x = 5

Check in 2nd equation.

2(5) -5(-1) = 15
10 + 5 = 15
15 = 15

Perhaps your 2nd problem expression should be written as

-13/(1-2x)

And disallowed is any value of x that makes (1 - 2x) equal to zero (division by zero is undefined).

Answer 2

There are many methods, for example:
2x - 5y = 15 , 2x = 15 + 5y. Now replace to the first equation:
y = 9 - (15 + 5y), y = 9 - 15 - 5y, 6y = -6, y = -1.
Replacing to the first, we have:
-1 = 9 - 2x, 2x = 9 + 1, 2x = 10, x = 5.
So the solution is: x = 5, y = -1.

Answer 3

First thing you need to do is to rewrite the set of equations like this:

2x + y = 9
2x - 5y = 15

Then solve the equation.
-(-6y) = -6
6y = -6
y = -1

Then solve for the x
(you can do the rest)

-13/1 - 2x
I am assuming you mean -13/(1-2x)
Then you can not have a value of x where 1-2x would be zero
which would be x=0.5

Answer 4

y = 9 - 2x
2x - 5y = 15

2x - 5(9 - 2x) = 15
2x - 45 + 10x = 15
12x - 45 = 15
3(4x - 15) = 15
4x - 15 = 5
4x = 20
x = 5

y = 9 - 2x
y = 9 - 2(5)
y = 9 - 10
y = -1

x = 5
y = -1

Answer 5

y = 9-2x
2x-5y = 15

2x-5(9-2x) = 15

2x-45-10x = 15

-45-8x = 15

-8x = 60

x = -7.5

y = 9-2x

y = 9+15

y = 24

Therefore, x = 9, and y = 24.

EDIT: uhh, sorry, can you make your second problem a little clearer?

All I can tell you is that -13/1-2x could mean (-13/1) - 2x, or -13/(1-2x).

Answer 6

y = 9 - 2x (eqn 1)
2x - 5y = 15 (eqn 2)
substracting (eqn 2) from (eqn 1), we have
6y = -6
hence, y= -1 Substituting this value in (eqn 1), we have
2x = 10
hence, x=5

therefore solution set is (5,-1)

Answer 7

the answer is 7. no 9. no 3. no 2. no 5. no 10........what's the question?

Answer 8

y= -1
x = 5