we know that
we will get solution of three system of equations when intersects at one point
For example:
x+2y-3z=-3
2x-5y+4z=13
5x+4y-z=5
These three system of equations has one solutions
so, it has unique solution
that is (2, -1 , 1)
And when planes are lying on one another
then we can get infinite solutions
For example:
x+2y-3z=-3
2x+4y-6z=-6
5x+4y-z=5
So, we will get value of x and y in terms of z
and z can be any value
so, x and y can also be any values
that's why there would be infinite number of solutions
