\(a,\left(4x-5\right)^2+7\left(4x-5\right)-8=0\\ \Rightarrow\left(4x-5\right)^2+8\left(4x-5\right)-\left(4x-5\right)-8=0\\ \Rightarrow\left(4x-5\right)\left(4x-5+8\right)-\left(4x-5+8\right)=0\\ \Rightarrow\left(4x+3\right)\left(4x-5-1\right)=0\\ \Rightarrow\left(4x+3\right)\left(4x-6\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=-\dfrac{3}{4}\\x=\dfrac{3}{2}\end{matrix}\right.\)
\(b,\left(x+3\right)^2\left(x^2+6x+1\right)=9\\ \Rightarrow\left(x^2+6x+1+8\right)\left(x^2+6x+1\right)-9=0\\ \Rightarrow\left(x^2+6x+1\right)^2+8\left(x^2+6x+1\right)-9=0\\ \Rightarrow\left[\left(x^2+6x+1\right)^2+9\left(x^2+6x+1\right)\right]-\left[\left(x^2+6x+1\right)+9\right]=0\\ \Rightarrow\left(x^2+6x+1\right)\left(x^2+6x+1+9\right)-\left(x^2+6x+1+9\right)=0\\ \Rightarrow\left(x^2+6x+10\right)\left(x^2+6x+1-1\right)=0\\ \Rightarrow\left(x^2+6x+10\right)\left(x^2+6x\right)=0\\ \Rightarrow x\left(x+6\right)\left(x^2+6x+10\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\x=-6\\\left(x+3\right)^2+1=0\left(vô.lí\right)\end{matrix}\right.\)
a: \(\Leftrightarrow\left(4x-5\right)^2+8\left(4x-5\right)-\left(4x-5\right)-8=0\)
\(\Leftrightarrow\left(4x-5\right)\left(4x-5+8\right)-\left(4x-5+8\right)=0\)
=>(4x-6)(4x+3)=0
=>x=3/2 hoặc x=-3/4
b: \(\Leftrightarrow\left(x^2+6x+9\right)\left(x^2+6x+1\right)-9=0\)
\(\Leftrightarrow\left(x^2+6x\right)^2+10\left(x^2+6x\right)=0\)
=>x(x+6)=0
=>x=0 hoặc x=-6
