Question

Q7Find the zeroes of the quadratic polynomial x

2

– x – 20 are

(a) 4, 5 (b) 2, - 4 (c) 3 ,4 (d) -4, 5​

Answer 1

Correct Question:

Find the zeroes of the polynomial x² - x - 20.

a) (4.5)

b) (2,-4)

c) (3,4)

d) (-4,5)

SoluTion:

x² - x - 20

By splitting middle term,

$\implies$ x² + 4x - 5x - 20 = 0

$\implies$ x (x + 4) - 5 (x + 4) = 0

$\implies$ (x - 5) (x + 4) = 0

$\implies$ (x - 5) = 0 and (x + 4) = 0

$\implies$ x = 5 and -4

Hence, zeroes of this Polynomial are -4 and 5

Option d) is correct.

Answer 2

${x}^{2} - x - 20 \\ \\ > {x}^{2} - 5x + 4x - 20 \\ \\ = > x(x - 5) + 4(x - 5) = 0 \\ \\ = > (x + 4)(x - 5) = 0$

Hence the Zeroes are -4 and 5.