Sunday, January 4, 2015

363: Without Solving for a Variable

Make similar questions ...

If  x² + y² = 196 and (x - y)² = 36, what is the value of xy?

  1. -116
  2. -80
  3. -8
  4. 80
  5. 160

3 comments:

  1. What is the value of 6x + 4y if x +3y = 8 and 2x - y = 10?
    Sure you can solve it like a system of equations, but one does not have to.

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  2. Two examples I love are:
    If x + (1/x) = 5, then what is the value of x^2 + (1/x^2) ?

    If x + y = 11 and xy = 15, find the value of x^2 + y^2

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  3. Eric ... not only do you not have to solve like a system, the solution is way harder that way.

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