Solution 2.1:2e
From Förberedande kurs i matematik 1
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| - | + | We expand the two quadratics using the squaring rule, and then sum the result  | |
| - | We expand the two quadratics using the squaring rule, and then sum the result  | + | |
| - | <math>   | + | {{Displayed math||<math>\begin{align}  | 
| + | (a+b)^2+(a-b)^2 &= (a^2+2ab+b^2)+(a^2-2ab+b^2)\\  | ||
&= a^2+2ab+b^2+a^2-2ab+b^2 \\  | &= a^2+2ab+b^2+a^2-2ab+b^2 \\  | ||
&= a^2+a^2+2ab-2ab+b^2+b^2\\  | &= a^2+a^2+2ab-2ab+b^2+b^2\\  | ||
| - | &= 2a^2 +2b^2  | + | &= 2a^2 +2b^2\,\textrm{.}  | 
| - | \end{align}  | + | \end{align}</math>}}  | 
| - | </math>  | + | |
| - | + | ||
| - | + | ||
Current revision
We expand the two quadratics using the squaring rule, and then sum the result
| \displaystyle \begin{align}
 (a+b)^2+(a-b)^2 &= (a^2+2ab+b^2)+(a^2-2ab+b^2)\\ &= a^2+2ab+b^2+a^2-2ab+b^2 \\ &= a^2+a^2+2ab-2ab+b^2+b^2\\ &= 2a^2 +2b^2\,\textrm{.} \end{align}  | 
