\(a,4x\left(x+1\right)+\left(3-2x\right)\left(3+2x\right)=15\\ 4x^2+4x+9-4x^2=15\\ 4x=15-9\\ 4x=6\\ x=6:4\\ x=1,5\)
\(b,3x\left(x-20012\right)-x+20012=0\\ 3x\left(x-20012\right)-\left(x-20012\right)=0\\ \left(3x-1\right)\left(x-20012\right)\\ \Rightarrow\left[{}\begin{matrix}3x-1=0\Rightarrow x=\dfrac{1}{3}\\x-20012=0\Rightarrow x=20012\end{matrix}\right.\)
a, \(4x^2+4x+\left(3^2-\left(2x\right)^2\right)-15=0\)
\(4x^2+4x+\left(9-4x^2\right)-15=0\)
\(4x^2+4x+9-4x^2-15=0\)
\(4x-6=0\)
=>\(x=\dfrac{6}{4}\)
b,
=(3x-1)(x-20012)=0
=> x =1/3 hoặc x = 20012
