Question

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

Answer 1

x² – 4x – 8 = 0

Comparing the above equation by ax² + bx + c = 0

 a = 1, b = –4, c = –8

`x = (-b ± sqrt(b^2 - 4ac))/(2a)`

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

`x = (4 ± sqrt(16 + 32))/2` 

`x = (4 ± sqrt(48))/2`

`x = (4 ± 6.928)/2`

x = 5.464 and –1.464 {approx}