what is the x,y algebra answer for x+y=3 x-y=5

Question

i need to find this answer out of my geometry class. it is being graded and i have no idea how to do it

Answer 1

Hey Rob -- often it's helpful simply to add the two expressions ... 2x= 8, x=4, y= -1

 

Sometimes subtracting will cancel out an x or y ... sometimes a formula has to be "rescaled" before adding or subtracting (I like to double or "cut in half") ... Best wishes, sir :)

Answer 2

x + y = 3  (eq. 1)

 

x - y = 5   (eq. 2)

 

let's solve for x using eq. 2

 

x = y + 5      (eq. 3)

 

let's substitute eq. 3 into eq. 1

 

(y + 5) + y = 3

 

2y + 5 = 3

 

subtract 5 from both sides

 

2y = -2

 

y = -1

 

let's substitute value of y into eq. 3 to get x

 

x = -1 + 5

 

x = 4

therefore, x = 4, y = -1

 

 

Answer 3

Brad's method works best for this problem.