Question

Solve x² + 7x = 7 and give your answer correct to two decimal places

Answer 1

Given quadratic equation is x² + 7x = 7

`=> x^2 + 7x - 7 = 0`

Comparing with `ax^2 + bx +c =0` we have a = 1, b = 7 and c = -7

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

`=> x = (-7 +- sqrt(7^2 - 4 xx 1 xx (-7)))/(2 xx1)`

`=> x = (-7+- sqrt77)/2`

`=> x  = (-7+- 8.77)/2`

`=> x = (-7+8.77)/2` and `x = (-7-8.77)/2`

`=> x = 1.77/2` and `x = (-15.77)/2`

`=> x = 0.885 and x = -7.885`

=> x = 0.89 and x = -7.89 (correct to two decimal places)