Q.

Find the zeroes of the following quadratics Polynomials.

(1)

Sol.

7x² + 4x – 20

7x²

+

4x

–

20

7x² + 4x – 20

=

7x²

–

20

+

140

14

10

–

x

x

=

x

(14x

–

10x)

=

7x²

+

14x

–

10x

–

20

=

7x

(x

+

2)

–

10

(x

+

2)

=

(x

+

2)

(7x

–

10)

(x + 2)

4

4

∴

x

=

–2

or

7x

=

10

∴

x

=

–2

or

x

=

∴

The zeroes of 7x² + 4x – 20 are –2 and

∴

(x + 2) and (7x – 10) are the factors of

7x² + 4x – 20

So, the value of 7x² + 4x – 20 is zero

When

(x + 2)

=

0

or

(7x – 10)

=

0

10

7

10

7

x + 2

=

0

or

7x – 10

=

0

∴

Q.

Find the zeroes of the following quadratics Polynomials.

(2)

Sol.

7m² – 84

7m² – 84

7m²

84

–

a² – b²

(a + b)

(a – b)

=

(m²

=

=

–

(m²)

∴

So, the value of 7m² – 84 is zero

When

=

0

or

=

0

∴

m

–

=

or

m

=

12

6

3

2

2

3

1

∴

– 12)

7

7

[

]

=

7

∴