b: \(\Leftrightarrow4x+1+3x+2-2\sqrt{\left(4x+1\right)\left(3x+2\right)}=\dfrac{1}{25}\left(x^2+6x+9\right)\)
=>1/25(x^2+6x+9)=7x+3-2căn(4x+1)(3x+2)
\(\Leftrightarrow x^2\cdot\dfrac{1}{25}+\dfrac{6}{25}x+\dfrac{9}{25}-7x-3=-2\sqrt{\left(4x+1\right)\left(3x+2\right)}\)
\(\Leftrightarrow\sqrt{4\left(4x+1\right)\left(3x+2\right)}=-\dfrac{1}{25}x^2-\dfrac{6}{25}x-\dfrac{9}{25}+7x+3=-\dfrac{1}{25}x^2+\dfrac{169}{25}x+\dfrac{66}{25}\)
\(\Leftrightarrow4\left(4x+1\right)\left(3x+2\right)=\left(\dfrac{1}{25}x^2-\dfrac{169}{25}x-\dfrac{66}{25}\right)^2\)
\(\Leftrightarrow x\in\left\{-0.13\right\}\)
c: \(\Leftrightarrow\sqrt{x+11}-\sqrt{x-4}=3\)
=>x+11+x-4-2căn (x+11)(x-4)=9
=>2căn(x+11)(x-4)=2x+7-9=2x-2
=>căn (x+11)(x-4)=x-1
=>x^2-2x+1=x^2-4x+11x-44
=>-2x+1=7x-44
=>-9x=-45
=>x=5
