13.已知函数f(x)=1−2xa+2x+1f(x)=\frac{1-{2^x}}{a+{2^{x+1}}}f(x)=a+2x+11−2x是奇函数.(1)求aaa的值,并求f(x)f(x)f(x)的定义域;(2)已知实数ttt满足f(t2−2t)+f(2t2−1)<0f(t^{2}-2t)+f(2t^{2}-1)<0f(t2−2t)+f(2t2−1)<0,求ttt的取值范围.