Question

Solve: 16x^2 − 80 = 0 using the quadratic formula

Round the answer to the nearest hundredth.


x = −0.45 and x = 0.45
x = −2.24 and x = 2.24
x = −8.94 and x = 8.94
x = −9.80 and x = 9.80

Answer 1

B

Explanation:

Using the quadratic formula with

a = 16, b = 0 and c = - 80, then

x = ( 0 ±
`√(0-(4(16)(-80))` / 32

= ±
`(√(5120) )/(32)`

x = -
`(√(5120) )/(32)` , x =
`(√(5120) )/(32)`

x = - 2.24, x = 2.24 ( to the nearest hundredth )

Answer 2

For this case we have the following quadratic equation:

`16x ^ 2-80 = 0`

Applying the quadratic formula we have:

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

Where:

`a = 16\\b = 0\\c = -80`

Substituting we have:

`x = \frac {-0 \pm \sqrt {0 ^ 2-4 (16) (- 80)}} {2 (16)}\\x = \frac {\pm \sqrt {4 (16) (80)}} {32}\\x = \frac {\pm \sqrt {5120}} {32}\\x = \frac {\pm71.55} {32}`

We have two roots:
`x_ {1} = \frac {-71.55} {32} = - 2.24\\x_ {2} = \frac {71.55} {32} = 2.24`

Answer:

Option B