Question

3x-y=40,2x-y=25 crass multiplication​

Answer 1

Answer:

Here, a1=3

b1 = -1

c1 = 40

and,

a2= 2

b2 =-1

c2 =25

a1/a2 = 3/2

b1/b2 = -1/-1 = 1/1

c1/c2 = 40/25=8/5

a1/a2 is not equal to b1/b2.

That means, it is unique solution.

By cross multiplication method,

x y 1

---------------------- = --------------------= ---------------------

b1c2-b2c1 c1a2-c2a1 a1b2- a2b1

x y 1

---------------------- = ---------------- = --------------------

(-1)(25)- (-1)(40) 40×2-25×3 3×(-1)-2×(-1)

x y 1

------------------ = ---------------- = ---------------

15 5 -1

x 1

x 1---------------- = ---------------

x 1---------------- = --------------- 15 -1

x= -15

y 1

1------------------ = ----------------

5 -1

y = -5

Hence, x = -15 and y =-5