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a+1/2(-a+b)=1/2a+1/2b


Hvorfor blir det ikke 1/2a^2+1/2ab

[tex]a+\frac{1}{2}\left(-a+b\right) = a-\frac{1}{2}a+\frac{1}{2}b = a\left(1-\frac{1}{2}\right)+\frac{1}{2}b = \frac{1}{2}a+\frac{1}{2}b[/tex]