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Using Cramer's Rule, Solve Following System Of Linear Equations. X+2y=7 3x-4y=-9 Can You Help?

3 Answers

maheen mirza Profile
maheen mirza answered
x + 2y =7
3x -4y = -9

A= 1 2
3 -4
!A!=(1)(-4)-(2)(3)
=-10
A1=7 2
-9 -4

!A1!=7*(-4)+(2)(9)
=-28+18
=-10
A2 =1 7
3 -9
!A2!=(-9)(1)-(7)(3)
=-9-21
=-30

X1=!A1! /!A!
=-10/-10
=1
X2=!A2!/!A!
=-30/-10
=3
X1=1 & X2=3 ANS.
hina Profile
hina answered
X+2y =7, 3x-4y =9

1. X+2y=7
2. 3x-4y=9

4x-2y=16
2(2x-y) =2(8)

2x-y=8

2x=y+8


x= y+8
2

Now put the value of x into 2,
3x-4y=9

3(y+8) =9
2

1 [(3y+24) =9] (multiply buy 2)
2

3y =9-24

3y=-15

y=- 5/2

Put this value of y in x= y+8
2

x= -5/2+8
2

So the answer is x=3
Anonymous Profile
Anonymous answered
X+2y=7
3x-4y=9
1   2   7
3   4   9
Det= 4-6
  D = -2
7   2
9   4
Dx= 28-18
    =10  therefore, x =10/-2 = -5
x= 1 then Dy = 1    7
  3    9
Dx= 9-21 = -12 therefore, y= -12/-2 = 6
(x, y) = (-5, 6) it is the final answer.

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Anonymous