Question

Someone please explain this step by step:

Answer 1

Answer:

  13

Step-by-step explanation:

Perhaps the most straightforward way to find the value of the given function is to first solve the equations for x and y. The results can be substituted into your expression to find the value you want.

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solving the system

We notice the y-coefficients are opposites, so we can eliminate the y-variable by adding the equations.

  (2x -y) +(x +y) = (3) +(1)

  3x = 4 . . . . . . simplify

  x = 4/3 . . . . . divide by 3

The value of y can be found from the second equation:

  4/3 +y = 1 . . . . substitute for x

  y = -1/3 . . . . . . subtract 4/3

expression value

The value of 8x-7y is found by substituting the x- and y-values into this expression:

  8(4/3) -7(-1/3) = 32/3 +7/3 = 39/3 = 13

The value of 8x-7y is 13.

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Additional comment

You can also work out what combination of the two equations will give 8x -7y. That turns out to be 5 times the first minus 2 times the second:

  5(2x -y) -2(x +y) = 5(3) -2(1)

  10x -5y -2x -2y = 15 -2

  8x -7y = 13

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The coefficients 5 and -2 are found by solving the system of equations ...

  a(2x -y) +b(x +y) ≡ 8x -7y   ⇒   {2a +b = 8, -a +b = -7}