Solving system of linear equations in two variables algebraically substitution/elimination. 1.y=6+-11 -2×-3y=-7 2.y=5×-7 -3×-2y=-12 3.-4×+y=6 -5×-y=21

2
by chens

2014-12-13T22:43:43+08:00
1. -2x-3y=-7
y=6+-11
-2x-3(6+-11)=-7
-2x-3(-5)=-7
-2x+15=-7
15+7=2x
22/2=2x/2
11=x
-2(11)-3y=-7
-22-3y=-7
-22+7=3y
-15/3=3y/3
-5=y

2. -3x-2y=-12
y=5x-7
-3x-2(5x-7)=-12
-3x-10x+14=-12
14+12=13x
26/13=13x/13
2=x
y=5(2)-7
y=10-7
y=3

3. -4x +y=6
-5x-y=21 ;-5x-21=y
-4x+(-5x-21)=6
-4x-5x-21=6
-9x=6+21
-27/9=9x/9
-3=x
-5(-3)-21=y
15-21=y
-6=y

2014-12-14T06:47:21+08:00

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1.) y=6+11
y=6-11
y=-5
-2x-3y=-7
-2x-3(-5)=-7
-2x+15=-7
-2x=-7-15
-2x=-22
-2x/-2=-22/-2
x=11
y=-5
(You can check it if it is truly correct or not. But, in Math, checking is just an option.)

2.) y=5x-7
-3x-2y=-12
-3x-2(5x-7)=-12
-3x-10x+14=-12
-13x + 14 =-12
-13x=-12-14
-13x =-26
-13x/-13=-26/-13
x = 2
y=5x-7
y=5(2)-7
y=10-7
y=3
So:
x=2 and y=3

3.) -4x + y=6
-5x-y=21
-4x-6=-y
(-4x/-1)+(-6/-1)=-y/-1
4x+6=y

-5x-y=21
-5x-(4x+6)=21
-5x-4x-6=21
-9x-6=21
-9x=21+6
-9x=27
-9x/-9=27/-9
x=-3
-4x+y=6
-4(-3)+y=6
12+y=6
12-6=-6
y=-6
x=-3 and y=-6