Question 205758
3^(x^2 -3x) =81=3^4
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x^2 -3x =4,,,,,,,exponents  must  be  equal
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x^2 -3x -4 =0
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(x-4)(x+1) =0
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x=4,-1
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check,,(4),,,3^((4)^2 -3(4)) =81
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3^(16-12) =3^4 = 81,,,,ok
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(-1),,,,,3^( (-1)^2 -3(-1))= 3^(1+3) = 3^4 =81,,,,ok