Posted by Ashley on Thursday, January 29, 2009 at 10:01pm.
Solving Systems by Substitution:
I need help learning how to do this problem step-by-step
algebra - Reiny, Thursday, January 29, 2009 at 10:04pm
your first equation says that
x = 1-4y
so "substitute" 1-4y wherever you see x in the other equation
2(1-4y) + 7y = 3
2 - 8y + 7y = 3
-y = 1
y = -1
next sub that y = -1 back into the first equation
x = 1 - 4(-1) = 1+4 = 5
algebra - Chopsticks, Thursday, January 29, 2009 at 10:12pm
x = 1-4y
Starting with the first equation
since x = 1 - 4y
Plug that in to the second equation
2 -8y + 7y = 3
2 - y = 3
2/2 - y = 3/2
- y = 3/2
Since why can't be negative, move the negative over to the other side
y = -3/2
Okay we found what Y is now plug that into the first equation
x = 1-4(-3/2)
x = 1 + 6
x = 7
so the answer is (7,-3/2)
I'm pretty sure this is right, but I hope a real tutor comes and say for sure
algebra - Chopsticks, Thursday, January 29, 2009 at 10:14pm
Oh sorry, I did my math wrong and Divided instead of subtracting.
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