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${\displaystyle \underset{3}{\overset{6}{}}}{e}^{2x}dx$

A$)\frac{1}{2}(e^{12}-e^6)$

B$)2(e^{12}-e^6)$

C$)e^{12}-e^6$

D$)\frac{1}{2}(e^6-e^{12})$