Question

Solve : x^2 - 2x - 15 = 0

Method of Quadratic equation.

Answer 1

Step-by-step explanation:

Use the quadratic formula

=

−

±

2

−

4

√

2

x=\frac{-{\color{#e8710a}{b}} \pm \sqrt{{\color{#e8710a}{b}}^{2}-4{\color{#c92786}{a}}{\color{#129eaf}{c}}}}{2{\color{#c92786}{a}}}

x=2a−b±b2−4ac

Once in standard form, identify a, b and c from the original equation and plug them into the quadratic formula.

2

−

2

−

1

5

=

0

x^{2}-2x-15=0

x2−2x−15=0

=

1

a={\color{#c92786}{1}}

a=1

=

−

2

b={\color{#e8710a}{-2}}

b=−2

=

−

1

5

c={\color{#129eaf}{-15}}

c=−15

=

−

(

−

2

)

±

(

−

2

)

2

−

4

⋅

1

(

−

1

5

)

√

2

⋅

1

x=\frac{-({\color{#e8710a}{-2}}) \pm \sqrt{({\color{#e8710a}{-2}})^{2}-4 \cdot {\color{#c92786}{1}}({\color{#129eaf}{-15}})}}{2 \cdot {\color{#c92786}{1}}}

x=2⋅1−(−2)±(−2)2−4⋅1(−15)

2

Answer 2

Step-by-step explanation:

SOLUTION

Given :

${x}^{2} - 2x - 15 = 0$

Find :

The roots of given equation.

SO :

$= > {x}^{2} - 5x + 3x - 15 = 0$

$= > x(x - 5) + 3(x - 5) = 0$

$= > (x - 5)(x + 3) = 0$

$= > x - 5 = 0 \: \: \: or \: \: \: x + 3 = 0$

$= > x = 5 \: \: \: or \: \: \: x = - 3$

Hence :

The roots of the given equation are 5, -3.