Question

Solve the following equation and give your answer correct to 3 significant figures:

5x² – 3x – 4 = 0

Answer 1

Given quadratic equation is 5x² – 3x – 4 = 0

Comparing it with ax² + bx + c = 0, we get

a = 5, b = – 3, c = – 4

∴ `x = (-b+- sqrt(b^2 - 4ac))/(2a)`

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

= `(3+-sqrt(9 + 16 xx 5))/10`

= `(3 +-sqrt89)/10`

= `(3 +- 9.434)/10`

= `(3 + 9.434)/10` or `(3 - 9.434)/10`

= 1.2434 or – 0.6434

= 1.243 or – 0.643