[tex] \large \boxed{ {a}^{2} + {b}^{2} = {(a + b)}^{2} - 2ab}[/tex]
The formula is derived from the (a+b)² which can be expanded as:
[tex] \large \boxed{ {(a + b)}^{2} = {a}^{2} + 2ab + {b}^{2} }[/tex]
Now since we only want a²+b² and not 2ab. We can add -2ab after (a+b)² which result in (a+b)²-2ab. This formula is pretty useful it comes to higher maths.
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