2x²+4x=3
2x²+4x+2=5
(√2 x + √2)²=√5²
√2 x + √2=√5或√2 x + √2=-√5
2x+2=√10或√2 x + √2=-√10
x=√10 /2 - 1或x=-√10 /2 - 1