maths help...............!?

Question

1) 3x-y=3 , 9x-3y= 9
2)0.2x+0.3y=1.3 , 0.4x+0.5y=2.3
3) 3x/2 - 5y/3 = -2 , x/3+y/2=13/6
Solve the following by substitution method
If u don't want to solve all plz solve at least 1.

Answer 1

3x - y = 3- - - - - -Equation 1
9x - 3y = 9- - - - -Equation 2
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Substitute method equation 1

3x - y = 3

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

- y = - 3x + 3

- 1(- y) = - 1(- 3x) + (- 1)(3)

y = - (- 3x) + (- 3)

y = 3x - 3

Insert the y value into equation 2

- - - - - - - - - - - - - - - - - - - - - - - - -

9x - 3y = 9

9x - 3(3x - 3) = 9

9x - (9x - 9) = 9

9x - 9x + 9 = 0

The coefficients and variables cancell. no solution

- - - - - - - - - - -s-

Answer 2

1)
3x - y = 3
9x - 3y = 9
You may have noticed that these two are exxentially the same equations. Multiply through the 1st on by 3 and you get the 2nd one. They are not independent, so the number of solutions is infinite.
2)
0.2x + 0.3y = 1.3
0.4x + 0.5y = 2.3
Multiplying the 2nd equation by 2, you get
0.8x + y = 4.6
y = 4.6 - 0.8x
3)
3x/2 - 5y/3 = -2
x/3 + y/2 = 13/6
x + 3y/2 = 13/2
x = 13/2 - 3y/2

Have fun!

Answer 3

Best way to solve simultaneous equations is be eliminating one quantity. You can also use determinants. But if you want it be substitution,
Your first question has infinite solutions as both are the same equation.
0.2x + 0.3y = 1.3 => 2x + 3y = 13
0.4x + 0.5y = 2.3 => 4x + 5y = 23
Now, 2(2x +3y) = 4x + 6y = 2(13) = 26
So, 4x = 26 - 6y
Substitute in other equation,
(26 - 6y) + 5y = 23
26 - 23 = 6y - 5y
y = 3
x = 2

Answer 4

well for the first one use 3x-y=3 and find y. subtract 3x from both sides and you are left with -y=3-3x. i would then take out the negative from the y and get y=3x-3. use this equation by plugging it into the other equation (9x-3y=9) good luck.

Answer 5

learn to do your work by yourself . don't go abt asking help for simple problems like these. good luck dude.