The trunk is 1, assuming that the branch is x and the small branch is x 2. According to the topic:1+x+x 2 = 91+0.
X 2+X-90 = 0, that is, (x-9)*(x+ 10)=0. Because the branches are not negative, the number of branches x=9, and each branch has 9 small branches according to the topic.