Question

For what value of a and b the pair of linear equations has Coincident lines on the graphical representation 2x-y= 5, (a-2b)x - (a+b)y =15

Answer 1

for having coincident lines
a1/a2=b1/b2=c1/c2
2/a-2b=-1/-a-b=-5/-15
2/a-2b=-5/-15. -1/-a-b=-5/-15
-30=-5a+10b. 15=5a+5b
5a-10b-30=0. -5a-5b+15=0

5a-10b=30
-5a-5b=-15
________
-15b=15
B=-1

therefore a=4