(2x+5)^2-(2x-5)^2=3x^2+41x-4
4x^2+20x+25-(4x^2-20x+25)=3x^2+41x-4
4x^2+20x+25-4x^2+20x-25=3x^2+41x-4
40x-3x^2-41x+4=0
-3x^2-x+4=0
a=-3, b=-1, c=4
\Delta=b^2-4ac=(-1)^2-4*(-3)*4=1+48=49
\sqrt\Delta=7
x_1=\frac{-b-\sqrt\Delta}{2a}=\frac{1-7}{2*(-3)}=\frac{-6}{-6}=1
x_2=\frac{-b+\sqrt\Delta}{2a}=\frac{1+7}{-6}=\frac{8}{-6}=-\frac{4}{3}=-1\frac{1}{3}