Carlos solved the system of equations below. What mistake did he make in his work?

2x + y = 5
x − 2y = 10

y = 5 − 2x
x − 2(5 − 2x) = 10
x + 10 + 4x = 10
5x + 10 = 10
5x = 0
x = 0

2(0) + y = 5
y = 5

Question

Carlos solved the system of equations below. What mistake did he make in his work?

2x + y = 5
x − 2y = 10

y = 5 − 2x
x − 2(5 − 2x) = 10
x + 10 + 4x = 10
5x + 10 = 10
5x = 0
x = 0

2(0) + y = 5
y = 5

jchick · Answer

a. He should have substituted 5 + 2x 	
	b. He did not distribute correctly 	
	c. He combined like terms incorrectly, it should have been 4x instead of 5x 	
	d. He made no mistake

jchick · Answer

y really equals -3

anonymous · Answer

hey texaschic101 can u finish helping me please

texaschic101 · Answer

first we will solve for y in the 1st equation
2x + y = 5
y = -2x + 5 or y = 5 - 2x
now we sub 5 - 2x in for y in the 2nd equation
x - 2y = 10
x - 2(5 - 2x) = 10 -- now we distribute through the parenthesis
x - 10 + 4x = 10 (MISTAKE HERE....distributed wrong

anonymous · Answer

2x + y = 5  --> y = -2x + 5                   
x - 2y = 10                                              
  x - 2(-2x + 5)= 10                                    
 x + 4x - 10= 10
  5x - 10 = 10
  5x = 20
  x = 4  
   Just plug four into your original equation for x and you'll get the y value