Question

Solve 5x² − 3x − 4 = 0 and give your answer correct to two significant figures.

Answer 1

Given:

5x² − 3x − 4 = 0

Where:

a = 5

b = −3

c = −4

`x = (-(-3)+- sqrt((-3)^2 - 4(5)(-4)))/(2(5))`

`= (3+- sqrt(9+80))/10`

`= (3+- sqrt89)/10`

`sqrt89`

= 9.43

`x = (3+-9.43)/10`

First root:

`x = (3+9.43)/10`

`=12.43/10`

= 1.243

= 1.2

Second root:

`x = (3-9.43)/10`

`= -6.43/10`

= −0.643

= −0.64

x = 1.2 or x = −0.64​