Worked example: Rewriting expressions by completing the square | High School Math | Khan Academy

Sal rewrites x²+16x+9 as (x+8)²-55 by completing the square.

High School Math on Khan Academy: Did you realize that the word "algebra" comes from Arabic (just like "algorithm" and "al jazeera" and "Aladdin")? And what is so great about algebra anyway? This tutorial doesn't explore algebra so much as it introduces the history and ideas that underpin it.

For free. For everyone. Forever. #YouCanLearnAnything

[queenofgrah]

Thank you very much! I love your simple and clear explanations

[b._.x]

can someone help me cause khan academy never replies, what happens if i have a question like ;

7xsq+4x+8 what do i do with the seven

[ShadowCrashed]

This makes zero sense. It's completely arbitrary and bs. Why do you subtract 64 when you just added it? What was the point? This is why i hate math. You just do things to get it to fit your weird logical pretzel. And you never really explain "why" you just plow through and we're just supposed to accept it. "Just do this because this is what you're supposed to do"