introductory algebra
posted by jose .
I had these problems on my test and for some reason got them wrong. Here are the problems:
Solve:
xy=9
x+y=1
The test states that the answer is (5,4)
I've checked ,y work and used substitution to solve this and still get x=4, y=5.
The second problem is:
Solve the system of equations by graphing.
a=1/2b+5
a4b=2
The answer is (6,2)
Again i got the reverse of this; (2,6).
I have been at these for several hours and want to pull my hair out. Are my answers really wrong or is it the test? HELP!
Thanks

xy=9
x+y=1
The test states that the answer is (5,4)
I've checked ,y work and used substitution to solve this and still get x=4, y=5.

Check your answer
4  5 = 9 yes
4 + 5 = 1, not +1 wrong
Now adding the two equations
2 x = 10
x = 5
then
5+y = 1
y = 4 
a=1/2b+5
a4b=2
substitute (1/2) b + 5 for a
(1/2) b + 5  4 b = 2
b + 10  8b = 4
7 b = 14
b = 2
then
a = 1 + 5 = 6