x = (- 7 ± √5) / 2
use the substitution u = 2x + 3
equation can now be written as
u² + 8u + 11 = 0
solve for u using the quadratic formula with a = 1, b = 8 and c = 11
u = ( - 8 ± √( 64 - 44 ) )/2
= ( - 8 ± √20 )/2 = ( - 8 ± 2√5 ) / 2 = - 4 ± √5
change the variable back into terms of x
2x + 3 = - 4 ± √5 ( subtract 3 from both sides )
2x = - 7 ± √5 ( divide both sides by 2 )
x = ( - 7 ± √5 ) / 2