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#cf2a1a91-89a8-48ac-8285-748ab1dc10cc基础fill_compute函数的单调性函数

12.若函数f(x)={(3a)x3,x7ax6,x>7f(x)=\left\{{\left.\begin{array}{l}{(3-a)x-3,x\leqslant 7}\\ {{a^{x-6}},x>7}\end{array}\right.}\right.单调递增,则实数aa的取值范围是 ___[94,3)[{\frac{9}{4},3})___.