2x+5y=15
-4x+7y=-13
2(2x+5y)=2(15) ok , how did we get the two on both sides ?!
x=5
2006-10-26 18:15:19 · 4 answers · asked by plz help me 1 in Science & Mathematics ➔ Mathematics
You put it there. The reason you multiply the equation by two is so that when you add it to the other equation, you will have only the y-variable remaining. Thus your next step is:
4x+10y=30
-4x+7y=-13
----------------
17y=17
y=1
2x+5(1)=15
2x=10
x=5
2006-10-26 18:20:08 · answer #1 · answered by Pascal 7 · 0⤊ 0⤋
2(2x+5y)=2*15
=>4x+10y=30
-4x+7y=-13
adding
17y=17
y=1
substituting
2x+5=15
=>2x=10
x=5
solution set{5,1}
2006-10-26 18:23:19 · answer #2 · answered by raj 7 · 0⤊ 0⤋
Because you have 2x
which means 2 times x
you have to multiply both sides by 2
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2006-10-26 18:18:09 · answer #3 · answered by Stacy M 4 · 0⤊ 0⤋
As long as what you do on one side you do it in the other, then it is OK. The 2 was made up, bit since the balance was maintained, it is OK to do it. The rest I cannot tell you because you did not post all the information.
2006-10-26 18:19:29 · answer #4 · answered by jasonheavilin 3 · 0⤊ 0⤋