Question

Multiply: (a) 5xfy and 8y x*​

Answer 1

Answer:

Step-by-step explanation:

Substitution method:

8x+5y=9      

∴y=

5

9−8x

​

       ....(1)

3x+2y=4         ...(2)

Substitute eq(1) in eq (2), we get

3x+2(

5

9−8x

​

)=4

Multiply by 5 on both sides, we get

15x+18−16x=20

⇒−x=2

⇒x=−2

Substitute x=−2 in eq (1), we get

y=

5

9−8(−2)

​

⇒y=

5

25

​

=5

So, (x,y)=(−2,5)

Cross-multiplication method:

8x+5y=9         ...(1)

So, a

1

​

=8,b

1

​

=5,c

1

​

=−9

3x+2y=4         ...(2)

So, a

2

​

=3,b

2

​

=2,c

2

​

=−4

∴x=

a

1

​

b

2

​

−a

2

​

b

1

​

b

1

​

c

2

​

−b

2

​

c

1

​

​

⇒x=

8(2)−3(5)

5(−4)−2(−9)

​

=

16−15

−20+18

​

=−2

y=

a

1

​

b

2

​

−a

2

​

b

1

​

c

1

​

a

2

​

−c

2

​

a

1

​

​

⇒y=

8(2)−3(5)

−9(3)−(−4)8

​

 =

16−15

−27+32

​

=5

So, (x,y)=(−2,5)