(3x + 1)2 - (3x - 1).(3x + 1) = 1
<=> (3x + 1).[(3x + 1) - (3x - 1)] = 1
<=> (3x + 1).(3x + 1 - 3x + 1) = 1
<=> (3x + 1).2 = 1
<=> 3x + 1 = 1/2
<=> 3x = -1/2
<=> x = -1/6
Vậy S = {-1/6}.
36x2 - 25 - x.(6x - 5) = 0
<=> (36x2 - 25) - x.(6x - 5) = 0
<=> [(6x)2 - 52] - x.(6x - 5) = 0
<=> (6x - 5).(6x + 5) - x.(6x - 5) = 0
<=> (6x - 5).(6x + 5 - x) = 0
<=> (6x - 5).(5x + 5) = 0
<=> 5.(6x - 5).(x + 1) = 0
<=> 6x - 5 = 0 hoặc x + 1 = 0
<=> x = 5/6 hoặc x = -1
Vậy S = {-1; 5/6}.
a)
\(\left(3x+1\right)^2-\left(3x-1\right)\left(3x+1\right)=1\)
\(\Rightarrow\left(9x^2+6x+1\right)-\left(9x^2-1\right)=1\)
\(\Rightarrow6x+2=1\)
\(\Rightarrow x=-\frac{1}{6}\)
Vậy pt có nghiệm là x = - 1 / 6
b)
\(36x^2-25-x\left(6x-5\right)=0\)
\(\Rightarrow\left(36x^2-25\right)-x\left(6x-5\right)=0\)
\(\Rightarrow\left(6x-5\right)\left(6x+5\right)-x\left(6x-5\right)=0\)
\(\Rightarrow\left(6x-5\right)\left(6x+5-x\right)=0\)
\(\Rightarrow\left(6x-5\right)\left(5x+5\right)=0\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=\frac{5}{6}\\x=-1\end{array}\right.\)
Vậy pt có nghiệm là x = 5 / 6 ; x = - 1