Solve using the multiplication principle first. Then use the elimination method: 7p+5q=2 8p-9q=17?

3 Answers

Oddman Profile
Oddman answered
Multiply the first equation by 8 and the second equation by 7.
  8(7p + 5q) = 8(2)
  56p + 40q = 16
  7(8p - 9q) = 7(17)
  56p - 63q = 119
Subtract the result of the second multiplication from the results of the first.
  (56p + 40q) - (56p - 63q) = 16 - 119
  103q = -103    (notice that p is eliminated)
  q = -1
Substitute this result into the first equation.
  7p + 5(-1) = 2
  7p = 7
  p = 1
The solution is (p, q) = (1, -1).
John McCann Profile
John McCann answered
-8(7p + 5q = 2)
7(8p -9q = 17)

-56p - 40q = - 16
56p - 63q = 119
------+
- 103q = 103
q = - 1
------

7p + 5(-1) = 2

7p - 5 = 2

7p = 7

p = 1
------

7(1) + 5(-1) = 2

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