Question

solve the following pair of linear equation 2x+y=4, 2x-y=4 by substitution method ,elimination method ,cross multiplication method

Answer 1

here ur answer
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by subsitution method
2x+y=4 eq 1
2x-y=4 eq2
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from eq 1
2x+y=4
y=4-2x eq 3
putting value of y in eq 2
2x-(4-2x)=4
2x-4+2x=4
2x+2x=4+4
4x=8
x=8/4=2
putting value of x in eq 3
y=4-2(2)
y=0
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by elimination method
2x+y=4
2x-y=4
4x=8
x=8/4=2
put value of x in eq 2
2x-y=4
2(2)-y=4
4-y=4
-y=4-4
y=0
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cross multiplication method
2x+y=4 eq 1
2x-y=4 eq 2
a1x+b1y+c1=0
a2x+b2y+c2=0
a1=2, b2=1,c2=4
a2=2,b2=-1,c2=4
a1/a2=2/2=1/1
b1/b2=1/-1
a1/a2 not=b1/b2
x/b1c2-b2c1=y/c1a2-c2a1=-1/a1b2-a2b1
1/8=1/0=-1/-4
x/8=-1/-4
x=2
y/0=-1/-4
y=0
hope its helps u

Answer 2

by subsitution method

2x+y=4 eq 1

2x-y=4 eq2

=======

from eq 1

2x+y=4

y=4-2x eq 3

putting value of y in eq 2

2x-(4-2x)=4

2x-4+2x=4

2x+2x=4+4

4x=8

x=8/4=2

putting value of x in eq 3

y=4-2(2)

y=0

by elimination method

2x+y=4

2x-y=4

4x=8

x=8/4=2

put value of x in eq 2

2x-y=4

2(2)-y=4

4-y=4

-y=4-4

y=0

cross multiplication method

2x+y=4 eq 1

2x-y=4 eq 2

a1x+b1y+c1=0

a2x+b2y+c2=0

a1=2, b2=1,c2=4

a2=2,b2=-1,c2=4

a1/a2=2/2=1/1

b1/b2=1/-1

a1/a2 not=b1/b2

x/b1c2-b2c1=y/c1a2-c2a1=-1/a1b2-a2b1

1/8=1/0=-1/-4

x/8=-1/-4

x=2

y/0=-1/-4

y=0