Of the following quadratic equations, which is the one whose roots are

1.	Of the following quadratic equations, which is the one whose roots are 2 and – 15 ?(a) x2 - 2x + 15 = 0(b) x2 + 15x - 2 = 0(c) x2 + 13x - 30 = 0(d) x2 - 30 = 0
Answer» (c) x² + 13x - 30 = 0 • x²- 2x + 15 = 0 ⇒ (x - 5)(x + 2) = 0 ⇒ x = 5, -2 • x² + 15x - 2 = 0. Solving x ≠ 2, -15 • x² + 13x - 30 = 0 ⇒ (x + 15)(x - 2) = 0 ⇒ x = -15, 2 • x² - 30 = 0 ⇒ x² = 30 ⇒ x = ±\(\sqrt{30}.\)

Of the following quadratic equations, which is the one whose roots are 2 and – 15 ?(a) x2 - 2x + 15 = 0(b) x2 + 15x - 2 = 0(c) x2 + 13x - 30 = 0(d) x2 - 30 = 0

Answer»

(c) x² + 13x - 30 = 0

• x²- 2x + 15 = 0

⇒ (x - 5)(x + 2) = 0 ⇒ x = 5, -2

• x² + 15x - 2 = 0. Solving x ≠ 2, -15

• x² + 13x - 30 = 0

⇒ (x + 15)(x - 2) = 0 ⇒ x = -15, 2

• x² - 30 = 0 ⇒ x² = 30 ⇒ x = ±\(\sqrt{30}.\)