# math

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PLEASE!!!!i need help on these 4:
*4y=15-3x
2y=3x+21

*4x=5y-14
y=-6x-9

*5x=4y-30
2x=3y=-12

*2/3y=10+4x
5x=1/3y-8

use linear combinations to solve the system of linear equations

thank you!!!

• math -

4y=15-3x ...(1)
2y=3x+21 ...(2)

Rewrite in standard form:
3x+4y-15=0....(1a)
3x-2y+21=0....(2a)

Subtract 2a from 1a to get
0x+6y - 36 = 0
from which y=6

Add 2(2a) to (1a) to get
9x+0y+27 = 0
from which x = -3

Check:
4y=24, 15-3x=24 OK
2y=12, 3x+21=12 OK

You can proceed the same way for the remaining problems. Post for answer verification if you wish, but it should not be necessary because a check with the original equations should have been done as in the example.

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