b. -75x+57=-75x+57
Step-by-step explanation:
If an equation after solving does not give the solution but give a true statement then the equation has infinitely many solution,
In option a.
57x+57=-75x-75
57x + 75x = -75 - 57
132x = -132
⇒ x = -1
i.e. it has only one solution,
In option b.
-75x+57=-75x+57
-75x + 75x = 57 - 57
0 = 0 ( True )
i.e. it has infinitely many solution.
In option c.
75x+57=-75x+57
75x + 75x = 57 - 57
150x = 0
⇒ x = 0
i.e. it has only one solution,
In option d.
-57x+57=-75x+75
-57x + 75x = 75 - 57
18x = 18
⇒ x = 1
i.e. it has only one solution.