Tìm x: (3x + 4)^2 - (3x - 1)(3x + 1) = 49

Bài 1: Tìm x
1. (3x+4)^2-(3x-1)(3x+1)=49
2. (3x-1)^2-(3x-2)^2=0
3. (2x+1)^2-(x-1)^2=0
4. 5x^2-5(x-1)^2-5=0
5. x^2-25-(x^2=5x)=0