Question

hich system of equations has no solution?

A.
3
x
−
y
=
2

9
x
−
3
y
=
6

B.
9
x
−
6
y
=
30

x
−
2
y
=
6

C.
4
x
−
y
=
1

8
x
−
2
y
=
2

D.
4
x
−
y
=
−
5

4
x
−
y
=
−

Answer 1

D

Reason: In D the two equations have the same left side (4x − y) but different right sides, so they cannot both be true for any x,y (they contradict each other). A and C are multiples (infinitely many solutions) and B has a unique solution.