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3 years ago

Please help. Algebra.

Mathematics

1 answer:

Artist 52 [7]3 years ago

5 0

Answer: (x,y) = (6,-3)

This means 6 goes in the first blank and -3 goes in the second blank.

=========================================================

Explanation:

Solve the second equation for x

x+8y = -18

x = -18-8y

We'll plug that into the first equation and isolate y. This is where substitution comes in.

5x + 7y = 9

5( x ) + 7y = 9

5( -18-8y ) + 7y = 9 ... replace x with -18-8y

-90-40y + 7y = 9

-90-33y = 9

-33y = 9+90

-33y = 99

y = 99/(-33)

y = -3

Use this y value to find x

x = -18-8y

x = -18-8(-3)

x = -18+24

x = 6

The solution is (x,y) = (6,-3)

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Checking the answer:

Let's check the first equation

5x+7y = 9

5(6)+7(-3) = 9 ... plug in (x,y) = (6,-3)

30-21 = 9

9 = 9 .... true equation

Do the same for the second equation as well

x+8y = -18

6 + 8(-3) = -18

6 - 24 = -18

-18 = -18 .... also true

Both equations are true when we plug in (x,y) = (6,-3), so the solution is confirmed.

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