Explications étape par étape:
1-
[tex]2 {x}^{2} + 3 = {x}^{2} + 4 \\ 2 {x}^{2} - {x}^{2} = 4 - 3 \\ {x}^{2} = 1 \\ x = 1 \: ou \: x = - 1[/tex]
2-
[tex] {(x + 2)}^{2} = 2 {x }^{2} + 4x \\ {x }^{2} +4x + 4 = 2 {x}^{2} + 4x \\ {x }^{2} = 4 \\ x = 2 \: ou \: x = - 2[/tex]
3-
[tex](x - 3)(x + 3) = 20 \\ {x}^{2} - 9 = 20 \\ {x}^{2} = 29 \\ x = \sqrt{29} \: ou \: x = - \sqrt{29} [/tex]
4-
[tex]4( {x}^{2} + 1) = 15 \\ 4 {x }^{2} + 4 = 15 \\ 4 {x}^{2} = 11 \\ {x}^{2} = \frac{11}{4 } \\ x = \frac{ \sqrt{11} }{2} \: ou \: x = - \frac{ \sqrt{11} }{2} [/tex]
