In which line is a mistake first made when solving the following system of equations by elimination for s?
2r + 7s = 11
r - 9s = -7
Line 1 2r + 7s = 11
2(r - 9s = -7)
Line 2 2r + 7s = 11
2r - 18s = -14
Line 3 -11s = -3
Line 4 s = 11/3
a.) Line 1
b.) Line 2
c.) Line 3
d.) Line 4
Math help please help me ?
2016-03-16 12:25 am
回答 (4)
2016-03-16 12:36 am
✔ 最佳答案
Let us look at simple solution:-2r + 7s = 11
-2r +18s = 14____ADD
25S= 25
S = 1
2R + 7 = 11
R = 2
R= 2 ,S =1
2016-03-16 12:35 am
Line 3 has a mistake.
2r + 7s = 11
-(2r - 18s = -14)
-------------------
25x = 25
x = 5
2r + 7s = 11
-(2r - 18s = -14)
-------------------
25x = 25
x = 5
2016-03-16 12:34 am
c) Line 3 is the first incorrect line
In line 2:
2r + 7s = 11
2r − 18s = −14
Now to get rid of r, you must SUBTRACT the 2nd equation from 1st giving:
(2r+7s)−(2r−18s) = (11)−(−14)
Line 3: 25s = 25
Line 4: s = 1
2016-03-16 12:28 am
c ) if this is to be a combination of lines 1 & 2
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