Prove that the following sets of three lines are concurrent: `x/a+y/b=1, x/b+y/a=1\ a n d\ y=x`

Prove that the following sets of three lines are concurrent: (x)/(a)=(y)/(b)=1,(x)/(b)+(y)/(a)=1 and y=x

Prove that the following sets of three lines are concurrent: 15 x-18 y+1=0,\ 12 x+10 y-3=0\ a n d\ 6x+66 y-11=0.

Prove that the following sets of three lines are concurrent: 15 x-18 y+1=0,\ 12 x+10 y-3=0\ a n d\ 6x+66 y-11=0.

Prove that the following sets of three lines are concurrent: 15x-18y+1=0,12x+10y-3=0 and 6x+66y-11=0

Prove that the parallelogram formed by the lines x/a+y/b=1,x/b+y/a=1,x/a+y/b=2 a n d x/b+y/a=2 is a rhombus.

Prove that the diagonals of the parallelogram formed by the lines x/a +y/b=1,x/b+y/a= 1, x/a + y/b = 2 and x/b + y/a = 2 are at right angles . Also find its area (a != b)

Prove that the following lines are concurrent. Also, find the point of concurrence : 5x -3y = 1, 2x+ 3y = 23, 42x + 21y = 257 .

Prove that the parallelogram formed by the lines x/a+y/b=1,x/b+y/a=1,x/a+y/b=2 and x/b+y/a=2 is a rhombus.

Prove that the diagonals of the parallelogram formed by the four lines : x/a +y/b=1,x/b+y/a= 1, x/a + y/b = -1 and x/b + y/a = -1 are at right angles .

Prove that the following lines are concurrent also find the point of concurrency. 3x-4y+5=0 " ...(1)" 7x-8y+5=0 " ...(2)" " "4x+5y=45 " ...(3)"