Question

Which shows the correct substitution of the values a, b, and c from the equation 0 = 4x2 + 2x – 1 into the quadratic formula below?

Quadratic formula: x =

Answer 1

For this case we have a quadratic equation given by:

`4x ^ 2 + 2x-1 = 0`

The roots are found by means of the quadratic formula below:

`x = \frac {-b \pm \sqrt {b ^ 2-4 (a) (c)}} {2 (a)}`

Where:

`a = 4\\b = 2\\c = -1`

So, we have:

`x = \frac {-2 \pm \sqrt {2 ^ 2-4 (4) (- 1)}} {2 (4)}`

Or in an equivalent way we have:

`x = \frac {-2 \pm \sqrt {2 ^ 2 + 4 (4) (1)}} {2 (4)}`

Answer:

The correct option will be:

`x = \frac {-2 \pm \sqrt {2 ^ 2-4 (4) (- 1)}} {2 (4)}`

Answer 2

a = 4, b = 2 and c= -1

Explanation:

Quadratic formula: x =√[-b ± v(b² - 4ac)]/2a

Here quadratic equation is 4x2 + 2x – 1

a = 4, b = 2 and c= -1

x =[-b ± √(b² - 4ac)]/2a

= [-2 ± √(2² - 4*4*-1)]/2*4

= [-2 ± √(4 + 16)]/8

= [-2 ± √20)]/8

= [-2 ± 2√5)]/8

= [-1 ± √5)]/4

x = [-1 ± √5)]/4