Question

which number ,when multiplied by its self, subtracted by one and divided by 2 results in 40 ?.

麻烦各位翻译一下，谢谢！！！

Answer 1

什么数乘以自己（也就是平方）后减去一再除以二等于40？
这是一道数学题，如果设某数为x的话，这句话的数学表述就是
(x²-1)/2=40,求x
答案是正负9

Answer 2

哪一个数,乘以自己,减去一然后除以2等于40?