Question

3x-4y=20:x+2y=5 solve by substituting method​

Answer 1

Step-by-step explanation:

3x - 4y = 20. eq.(i)

x + 2y = 5. eq.(ii)

in eq.(ii)

x + 2y = 5

x = 5 - 2y. eq.(iii)

substitute the valie of x in eq. (i)

3 (5-2y) - 4y = 20

15 - 6y - 4y = 20

15 - 10y = 20

- 10y = 20 - 15

y = 5/-10

y = -2

put the value of y in eq. (iii)

x = 5 - 2y

x = 5 - 2 ( -2)

x = 5 + 4

x = 9

Answer 2

Question : Solve the question by the method of elimination by substitution :-

Question :-

3x-4y=20

x+2y=5

Answer

Substitution or elimination?

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Substitution:

1.3x-4y=20

2.x%2B2y=5

From eq. 2,

x=5-2y

Substitute into eq. 1,

3%285-2y%29-4y=20

15-6y-4y=20

-10y=5

highlight%28y=-1%2F2%29

Then from eq. 2,

x=5-2%28-1%2F2%29

x=5%2B1

highlight%28x=6%29

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.

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Elimination:

1.3x-4y=20

2.x%2B2y=5

Multiply eq. 2 by (2) and add to eq. 1,

3x-4y%2B2x%2B4y=20%2B10

5x=30

highlight_green%28x=6%29

Then use either equation to solve for y.

18-4y=20

-4y=2

highlight_green%28y=-1%2F2%29