а) \( 5^2 - x^2 = 0 \)
\( (5 - x)(5 + x) = 0 \)
\( 5 - x = 0 \) или \( 5 + x = 0 \)
\( x = 5 \) или \( x = -5 \)
б) \( 9 - 36y^2 = 0 \)
\( 9(1 - 4y^2) = 0 \)
\( 1 - 4y^2 = 0 \)
\( (1 - 2y)(1 + 2y) = 0 \)
\( 1 - 2y = 0 \) или \( 1 + 2y = 0 \)
\( y = \frac{1}{2} \) или \( y = -\frac{1}{2} \)
в) \( (5 - y)^2 - y(y + 2,5) = 25 \)
\( 25 - 10y + y^2 - y^2 - 2,5y = 25 \)
\( -12,5y = 0 \)
\( y = 0 \)