Question

solve the following system of equations x+2y=4. 2x+5y=9

Answer 1

x+2y=4 -------@1
2x+5y=9---------@2

multiply @1 by 2 you get
2(x+2y=4)
2x+4y=8--------@1
now subtract @1 from @2
2x+4y=8
(-) 2x+5y=9
change the sign of @2
so it becomes -2x-5y=-9-------@2
2x+4y=8
-2x-5y=-9
so now 2x and -2x gets cancelled
4y-5y=8-9
-1y=-1
so we get y=1
now apply y=1 in @2
we get
2x+5×1=9
2x+5=9
2x=9-5
2x=4
x=4/2
x=2
now we get x=2 & y=1