Question

3. If one of the factor of x^2 + x – 20 is (x + 5). Find the other *
A. x – 4
B. x - 3
C. x - 7
D. 0

Answer 1

Answer:

A. x-4

Step-by-step explanation:

Let (x−a) be the other factor.

Now, (x+5),(x−a) are factors of the quadratic equation x

2

+x−20

Thus,

(x+5)(x−a)=x

2

+x−20

=>x

2

−ax+5x−5a=x

2

+x−20

=>x(5−a)−5a=x−20

Now, considering the co-efficients of x on the both sides,

5−a=1

=>a=5−1=4

Therefore the other factor is (x−4)

Answer 2

Answer:

4

Step-by-step explanation:

x2+x-20=0

x2+(5-4)x-20=0

x2+5x-4x-20=0

x(x+5) -4(x+5)=0

(x+5)(x-4)=0

other is x-4