2x + y = 7
5x + y = 9
Solve the system of equations.

Question

2x + y = 7
5x + y = 9
Solve the system of equations.

texaschic101 · Answer

do you prefer substitution or elimination ?

anonymous · Answer

Elimination :)

texaschic101 · Answer

2x + y = 7
5x + y = 9 --->(-1)
-------------
2x + y = 7
-5x - y = -9 (result of multiplying by -1)
------------add
-3x = -2
x = 2/3

now sub 2/3 in for x in either equation to find y
2x + y = 7
2(2/3) + y = 7
4/3 + y = 7
y = 7 - 4/3
y = 21/3 - 4/3
y = 17/3

check..
5x + y = 9
5(2/3) + 17/3 = 9
10/3 + 17/3 = 9
27/3 = 9
9 = 9 (correct)

x = 2/3 and y = 17/3

I always hated the ones with fractions...lol

anonymous · Answer

What if it's a problem like this?
Find the solution to the equations.

2x - y = -3 
x + y = 0