Solve for x in 2x + 20sqrt(x) - 42 = 0?

1 Answer
Apr 14, 2018

Please look below.

Explanation:

This may look complicated but can be solved like a quadratic equation if we let u = sqrtx

2x + 20sqrtx - 42 = 0

2u^2 + 20u - 42 = 0

u^2 + 10u - 21 = 0

Using the quadratic equation:

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

u = (-10 +-sqrt(10^2 - 4xx1 xx -21))/(2 xx 1)

u = (-10 +-sqrt(184))/(2)

u = (-10 +-2sqrt(46))/(2)

u = -5 +-sqrt(46)

Therefore:

sqrt(x) = sqrt(-5+-sqrt(46))