What is the solution to the above system of equations?

2x+5y=-4
4x-5y=22

A. (3,-2)
B. (13/3, -24/3)
C. (-2,3)
D. (3,2/5)

Respuesta :

Answer:   A. (3,-2)

Step-by-step explanation:

Solve by Substitution :

// Solve equation [2] for the variable  x  

 

 [2]    4x = 5y + 22

 [2]    x = 5y/4 + 11/2

// Plug this in for variable  x  in equation [1]

  [1]    2•(5y/4+11/2) + 5y = -4

  [1]    15y/2 = -15

  [1]    15y = -30

// Solve equation [1] for the variable  y  

  [1]    15y = - 30  

  [1]   y = - 2  

// By now we know this much :

   x = 5y/4+11/2

   y = -2

// Use the  y  value to solve for  x  

   x = (5/4)(-2)+11/2 = 3  

Solution :

{x,y} = {3,-2}