Tìm x, biết: a) (3x + 4)^2 – (3x – 1)(3x + 1) = 49 b) x^2 -4x+4 =9(x-2)

a) 

 3x+42–3x–13x+1=499x2+24x+16−9x2−1=49         9x2+24x+16−9x2+1=49                                             24x+17=49                                                         24x=32                                                                x=43

Vậy x=43

b) 

x2–4x+4=9x–2x2–4x+4−9x–2=0x−2−29x–2=0x−2x−2−9=0x−2x−11=0⇒x−2=0x−11=0⇒x=2x=11

Vậy x∈2;  11