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how do you solve the following system by substitution4y=-5x , 5x+8y=20

0 votes

solve system using any method

4y=-5x

5x+8y=20

asked Dec 2, 2013 in ALGEBRA 2 by dkinz Apprentice
reshown Dec 2, 2013 by goushi

1 Answer

0 votes

Substitution method:

4y = -5x

Divide to each side by 4.

4y/4 = -5x/4

y = -5x/4 -------> (1)

5x+8y = 20

From (1) substitute the y value in (1).

5x+8*-5x/4 = 20

5x-10x = 20

-5x = 20

Divide to each side by negitive 5.

-5x/-5 = 20/-5

x = -4

Substitute the x value in (1).

y = (-5*-4)/4

y = 20/4

y = 5

Solution is x = -4, y= 5.

answered Dec 2, 2013 by william Mentor

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