Answer:
1. 9 or -9
2. 3.6 or -3.6
3. 12 and -12
4. The quadratic function has no real roots.
Step-by-step explanation:
1. Solve x² -81 = 0
x² -81 = 0
x² = 81
x = ±√81
x = 9 or x = -9
2. solve 2x² - 26 = 0
2x² - 26 = 0
2x² = 26
x² = 13
x = ±√13
∴ x = 3.6 or x = -3.6
3. f(x) = x² - 144
let f(x) = 0
x² - 144 = 0
x² = 144
x = ±√144
x = 12 and x = -12
4. f(x) = x² + 25
let f(x) = 0
x² + 25 = 0
x² = -25
x = ±√(-25)
There is no square root of a negative number. Its square is not a real number.
