# Solve the simultaneous equations 5x + y = 21 x – 3y = 9 x = ________ y = ________

Question

Solve the simultaneous equations

5x + y = 21
x – 3y = 9

x = ________
y = ________

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1 year 2021-09-02T07:18:55+00:00 2 Answers 0 views 0

## Answers ( )

5x+y=21……equation 1

x-3y=9……equation 2

from1:y=21-5x…..equation 3

substitute y by 21-5x in equation 2

x-3(21-5x)=9

x-63+15x=9

x+15x=9+63

16x=72(we divide both sides by 16)

16÷16=72÷16

therefore x=9/2 or x=4,5

substitute x by 4,5 or 9/2 in equation 3

y=21-5(9/2) or y=21-5(4,5)

y=-3/2 or y=-3/2

prove

5(9/2)-3/2=21

-3/2-3(9/2)=9
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