Question

solve the following equation by using the substitution method 2x+3y=9 3x+4y=5

Answer 1

equation first : 2x+3y=9
equation second : 3x+4y=5

from eq 1 we get : 2x + 3y =9 
                               3y= 9 - 2x
                              y=9 - 2x / 3
substituting y = 9 - 2x /3 in eq 2, we get :
             
=> 3x + 4 (9-2x /3) = 5
=> 3x+(36-8x/3) = 5
=> (9x+36-8x)/3 = 5
=> (x+36)/3 = 5
=>  x+36 = 15
=> x = -36+15
=> x = -21   
                                         

Answer 2

Answer:

given :

2x + 3y = 9

3x + 4y = 5

Multiplying equation (i) by 3 and (ii) by 2 and then subtracting, we get

y = 17

Putting the value of y = 17 in equation (i)

2x + 3 x 17 = 9

⇒ 2x + 51 = 9

⇒ 2x = 9 – 51

⇒ 2x = -42

⇒ x = -21

Hence the required solution is x = -21 and y = 17.