Question

what is the number that should be added to x^2-20x to complete the square?????

Answer 1

You MUST get this idea stuck in your head...

(x + a)^2 = x^2 + 2ax + a^2

Study and ponder that 'a' on the right hand side and you should see it.

Answer 2

10

Answer 3

?

Answer 4

You almost see it.

2a = -20 then a = -10
You no wneed to find a^2.

Answer 5

100?

Answer 6

????

Answer 7

Why do you doubt? You have it! Good work.