9514 1404 393
Answer:
(x, y) = (1/2, 5)
Step-by-step explanation:
We observe that the y-terms have coefficients 7 and -14. If we want to eliminate the y-terms, we need to multiply 7 by a factor that makes it be the opposite of -14. That factor will be -(-14)/7 = 2.
After multiplying the first equation by 2, we have ...
- 16x +14y = 78
- 4x -14y = -68
Adding these two equations gives ...
20x = 10
Solving for x, we need to divide by 20:
x = 10/20 = 1/2
Substituting this into the first equation, we get ...
8(1/2) +7y = 39
7y = 35 . . . . . . subtract 4
y = 35/7 = 5 . . . divide by 7
Then the solution is (x, y) = (1/2, 5).
_____
<em>Check</em>
We used the first equation to find y, so we know the x- and y-values satisfy the first equation. We need to check the result using the second equation.
4(1/2) -14(5) = -68
2 -70 = -68 . . . . . . . true; result checks OK
