Question

Fill in the blank

$\begin{array}{ccc}25& 81& \left(196\right)\\ 16& 49& \left(121\right)\\ 64& 100& (-)\end{array}$

Answer 1

The series follows the rule:
The third number in each row is the square of the sum of the square roots of the first and second numbers.
$(\sqrt{a}+\sqrt{b}{)}^2=c$
$\sqrt{25}=5;\sqrt{81}=9;5+9=14;{14}^2=196$
$\sqrt{16}=4;\sqrt{49}=7;4+7=11;{11}^2=121$
$\sqrt{64}=8;\sqrt{100}=10;8+10=18;{18}^2=324$