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3 years ago

2x-9y=8 -5x+8y=20 find x and y

Mathematics

1 answer:

Nataly [62]3 years ago

7 0

9514 1404 393

Answer:

(x, y) = (-244/29, -80/29)

Step-by-step explanation:

A graph (2nd attachment) shows the solution to be non-integer values, so we'll use the "cross multiply method" to find the solution.

Rewriting the equations to general form gives ....

2x -9y -8 = 0

5x -8y +20 = 0

Writing the coefficients in two rows of four, we have the table as in the first attachment. (The first column is repeated as the 4th column.)

Now, the cross product differences are formed. Each "orange" cross product difference is the difference of the product of "blue" coefficients and the product of "yellow" coefficients. The same formula is copied to the right.

These difference numbers go, left to right, into the form ...

1/p1 = x/p2 = y/p3 . . . . . . where p1, p2, p3 are the cross product differences

In this problem, the solution is ...

x = -244/29 ≈ -8.414

y = -80/29 ≈ -2.759

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