Question

Which of the following quadratic equation has roots –3 and –5?

Options

• X² – 8X + 15 = 0

• X² – 8X – 15 = 0

• X² + 8X + 15 = 0

• X² + 8X – 15 = 0

Answer 1

X² + 8X + 15 = 0

Explanation:

The roots of the quadratic equation x² + 8x + 15 = 0 are

x² + 5x + 3x + 15 = 0   ...`((5 xx 3 = + 15),(5 + 3 = + 8))`

x(x + 5) + 3(x + 5) = 0

(x + 5)(x + 3) = 0

∴ x + 5 = 0

x = –5

∴ x + 3 = 0

x = –3