Question

Find a if x-5 is a factor of x^ -4x^ + ax +60​

Answer 1

a = - 17

Explanation:

Let, f(x) = x³ - 4x² + ax + 60

Since (x - 5) is a factor of f(x), then x = 5 is a solution of f(x) = 0

⇒ f(5) = 0

⇒ 5³ - 4 × 5² + a × 5 + 60 = 0

⇒ 125 - 100 + 5a + 60 = 0

⇒ 5a + 85 = 0

⇒ 5a = - 85

⇒ a = - 85 / 5

⇒ a = - 17

Answer 2

Answer:

Correct option is

A

15

Since, (x -2) is one factor of x

2

+ax−6=0

⇒2

2

+a(2)−6=0

⇒2a=2⇒a=1 ...(i)

Again as (x -2) is factor of x

2

−9x+b=0

⇒2

2

−9(2)+b=0

⇒b=14 ...(ii)

Now, a+b=1+14=15

Hence, Option A is correct.