(2x+5)²-(3-2x)²-3(x-2)(x+2)=4(5x+3)
4x^2+20x+25-(9-12x+4x^2)-3(x^2-4)=20x+12
4x^2+20x+25-9+12x-4x^2-3x^2+12-20x-12=0
-3x^2+12x+16=0
rozwiązanie równania kwadratowego
ax + bx + c = 0
\Delta=b^2-4ac=144-4*(-3)*16=336
\sqrt\Delta=\sqrt{336}=\sqr{16*21}=4\sqrt{21}
x_1=\frac{-b-\sqrt\Delta}{2a}=\frac{-12-4\sqrt{21}}{-6}=\frac{-4(3+\sqrt{21})}{-6}=\frac{2}{3}(3+\sqrt{21})
x_2=\frac{-b+\sqrt\Delta}{2a}=\frac{-12+4\sqrt{21}}{-6}=\frac{-4(3-\sqrt{21})}{-6}=\frac{2}{3}(3-\sqrt{21})