Question

Solve for x the quadratic equation x² - 4x - 8 = 0.  
Give your answer correct to three significant figures. 

Answer 1

`x^2 - 4x - 8 = 0`

Comparing the above equation by `ax^2 +bx + c = 0`

 a = 1 , b = -4 , c = - 8

`x = (-2 +- sqrt(b^2 -4 ac))/(2a)`

`x = (4+- sqrt(-4)^2 - 4 xx 1 xx (-8))/(2xx1)` 

`x =(4+- sqrt(16+32))/2` 

`x = (4+- sqrt(48))/2`

`x = (4+- 6.928)/2`

x = 5.46 and -1.46 {approx}