$\frac{1}{16}{a}^2-<!--\; -\; -->\frac{1}{25}=0$
$(\frac{1}{4}a{)}^2-<!--\; -\; -->(\frac{1}{5}{)}^2=0$
$(\frac{1}{4}a-<!--\; -\; -->\frac{1}{5})(\frac{1}{4}a+\frac{1}{5})=0$ | * 20
(5a − 4)(5a + 4) = 0
5a − 4 = 0
5a = 4
$a=\frac{4}{5}$
или
5a + 4 = 0
5a = −4
$a=-<!--\; -\; -->\frac{4}{5}$
Ответ: $-<!--\; -\; -->\frac{4}{5};\frac{4}{5}$.

$\frac{4}{49}{b}^2-<!--\; -\; -->\frac{16}{121}=0$
$(\frac{2}{7}b{)}^2-<!--\; -\; -->(\frac{4}{11}{)}^2=0$
$(\frac{2}{7}b-<!--\; -\; -->\frac{4}{11})(\frac{2}{7}b+\frac{4}{11})=0$ | * 77
(22b − 28)(22b + 28) = 0
22b − 28 = 0
22b = 28
$b=\frac{28}{22}=\frac{14}{11}=1\frac{3}{11}$
или
22b +28 = 0
22b = −28
$b=-<!--\; -\; -->\frac{28}{22}=-<!--\; -\; -->\frac{14}{11}=-<!--\; -\; -->1\frac{3}{11}$
Ответ: $-<!--\; -\; -->1\frac{3}{11};1\frac{3}{11}$.

$\frac{9}{16}{c}^2-<!--\; -\; -->\frac{81}{100}=0$
$(\frac{3}{4}c{)}^2-<!--\; -\; -->(\frac{9}{10}{)}^2=0$
$(\frac{3}{4}c-<!--\; -\; -->\frac{9}{10})(\frac{3}{4}c+\frac{9}{10})=0$ | * 20
(15c − 18)(15c + 18) = 0
15c − 18 = 0
15c = 18
$c=\frac{18}{15}=\frac{6}{5}=1\frac{1}{5}$
или
15c + 18 = 0
15c = −18
$c=-<!--\; -\; -->\frac{18}{15}=-<!--\; -\; -->\frac{6}{5}=-<!--\; -\; -->1\frac{1}{5}$
Ответ: $-<!--\; -\; -->1\frac{1}{5};1\frac{1}{5}$.

$\frac{36}{1225}{d}^2-<!--\; -\; -->\frac{64}{441}=0$
$(\frac{6}{35}d{)}^2-<!--\; -\; -->(\frac{8}{21}{)}^2=0$
$(\frac{6}{35}d-<!--\; -\; -->\frac{8}{21})(\frac{6}{35}d+\frac{8}{21})=0$ | * 105
(18d − 40)(18d + 40) = 0
18d − 40 = 0
18d = 40
$d=\frac{40}{18}=\frac{20}{9}=2\frac{2}{9}$
или
18d + 40 = 0
18d = −40
$d=-<!--\; -\; -->\frac{40}{18}=-<!--\; -\; -->\frac{20}{9}=-<!--\; -\; -->2\frac{2}{9}$
Ответ: $-<!--\; -\; -->2\frac{2}{9};2\frac{2}{9}$.