What term should be added to (a^2 - 2ab) to make it a perfect square?
b
b^2
a^2
2ab
What term should be substracted to a2+2ab to make it a perfect square?
What number should be added to x2+6x to make it a perfect square?
What number should be added to 9x2 + 18 x to make it a perfect square?