Question

How do I solve this using the substitution method 3x+4y=0 2x+5y=7

Answer 1

Answer:

x=4

y=-3

Step-by-step explanation:

3x+4y=0

2x+5y=7

Change 3x+4y=0 into y= -3/4x

so substitute for y

2x-15/4x=7

-1 3/4x = 7

x=-4

substitue x for y and get

-3/4 * 4

y=-3

Answer 2

Answer: x = - 4

y = 3

Step-by-step explanation:

The given system of simultaneous equations is expressed as

3x+4y=0 - - - - - - - - - - - - -1

2x+5y=7- - - - - - - - - - - - - - - 2

From equation 1, we would make x the subject of the formula. Firstly, we would subtract 4y from the Left hand side and the right hand side of the equation. It becomes

3x +4y - 4y = 0 - 4y

3x = - 4y

We would divide the Left hand side and the right hand side of the equation by 3. It becomes

3x/3 = - 4y/3

x = - 4y/3

Substituting x = - 4y/3 into equation 2, it becomes

2 × - 4y/3 +5y = 7

- 8y/3 + 5y = 7

(- 8y + 15y)/3 = 7

7y/3 = 7

Cross multiplying, it becomes

7y = 21

Dividing the left hand side and the right hand side of the equation by 7, it becomes

7y/7 = 21/7

y = 3

Substituting y = 3 into x = - 4y/3, it becomes

x = - 4× 3/3

x = - 4