a: \(\Leftrightarrow10\left(x-3\right)^2+4\left(x-6\right)^2=6\left(x+9\right)^2-20\left(13x-1\right)\)
\(\Leftrightarrow10x^2-60x+90+4x^2-48x+144=6x^2+108x+486-260x+20\)
=>14x^2-108x+234=6x^2-152x+506
=>8x^2+44x-272=0
=>\(x=\dfrac{-11\pm\sqrt{665}}{4}\)
b: =>7(x-2)^2-(x+1)^2=9(x-4)(x-6)
=>7x^2-28x+28-x^2-2x-1=9(x^2-10x+24)
=>9x^2-90x+216=6x^2-30x+27
=>3x^2-60x+189=0
=>x^2-20x+63=0
=>\(x=10\pm\sqrt{37}\)
c: \(\Leftrightarrow\left(\dfrac{x+1}{94}+1\right)+\left(\dfrac{x+2}{93}+1\right)+\left(\dfrac{x+3}{92}+1\right)=\left(\dfrac{x+4}{91}+1\right)+\left(\dfrac{x+5}{90}+1\right)+\left(\dfrac{x+6}{89}+1\right)\)
=>x+95=0
=>x=-95
