Решите уравнение (3+6x)(3x-9)=0 25 - x во 2 степени =0

( 3 + 6x)( 3x - 9) = 0
9x - 27 + 18x² - 54x = 0
18x² - 45x - 27 = 0
D = b² - 4ac = ( - 45)² - 4 × 18 × ( - 27) = 2025 + 1944 = 3969 = 63²
x₁ = 45 + 63 / 36 = 108 / 36 = 3
x₂ = 45 - 63 / 36 = - 18 / 36 = - 0,5

25 - x² = 0
- x² + 25 = 0
x² - 25 = 0
D = b² - 4ac = 0 - 4 × 1 × ( - 25) = 100 = 10²
x₁ = 0 + 10 / 2 = 5
x₂ = 0 - 10 / 2 = - 5