Posted by jason on Monday, June 29, 2009 at 11:44pm.
solve by substitution
What is the solution of the system?
is this correct?
math - Marth, Tuesday, June 30, 2009 at 9:48am
You can check your work by using the values you found for x and y in the equations to see if they match.
7(7) + 6(-5) = 7
49 - 30 = 7
19 = 7
7 = 58 - 9*(-5)
7 = 58-45
7 = 13
Clearly, something is wrong.
Substitute 58-9y for x in 7x+6y=7 (because x = 58-9y)
7(58-9y) + 6y = 7
406 - 63y + 6y = 7
399 - 57y = 0
399 = 57y
y = 7
x = 58 - 9y
x = 58 - 9*7
x = 58 - 63
x = -5
The answer is (-5,7). Always (x,y).
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