Question

$\sqrt{a}+ \sqrt{4}= \sqrt{81}$
чему равно а=?
49 или 7?

Answer 1

√ a + √ 4 = √ 81
√ a = √ 81 - √ 4 = 9 - 2 = 7 
( √ a )² = 7²
a = 49 

Answer 2

$\sqrt{a}+ \sqrt{4}= \sqrt{81} \\ \\ \sqrt{a} = \sqrt{81} - \sqrt{4} \\ \\ \sqrt{a} = 9 - 2 = 7 \\ \\ (\sqrt{a})^2 = 7^2 \\ \\ a = 49$

Ответ: a = 49