Question

8 square -21x-9=0 find the roots by factorisation method

Answer 1

8 x² - 21 x - 9 = 0

==> 8 x² -24 x + 3 x - 9 = 0

==> 8 x ( x - 3 ) + 3 ( x - 3 ) = 0

==> ( x - 3 )( 8 x + 3 ) = 0

$\underline{\textsf{ANSWER}}$

Either x - 3  = 0

==> x = 3

or : 8 x + 3 = 0

==> 8 x = -3

==> x = -3 / 8

Hope it helps

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Answer 2

Given,

p(x) = 8x^2 -21x-9=0

Now to solve a quadratic equation we can use 3 methods =>

1)Completing Square Method,

2)Middle term Split method, and

3)By Quadratic formula.

Here we will solve the equation by using the factorization method =>

8x^2 -21x-9=0

=>8x^2 -24x + 3x -9 =0

=> 8 x ( x - 3 ) + 3 ( x - 3 ) = 0

=> ( x - 3 )( 8 x + 3 ) = 0

Hence we have=>

Either x = 3 or x =-3/8

Extra information

In quadratic formula method =>

d = discriminant (decides the nature of roots or zeroes of a quadratic equation.

a)when d = 0

then the quadratic equation will have the same real and equal roots.

b)when d>0

then the quadratic equation will have two real and distinct roots.

c)when d<0

then the quadratic equation will have no real roots i.e it will have imaginary roots.