TenTukan himpunan Dari 2x2-x-15=0 dengan cara kuadrat sempurna :)

[tex]\displaystyle 2x^2-x-15=0 \\ 2(x^2-\frac{1}{2}x)-15=0 \\ 2(x^2-2.\frac{1}{4}x+\frac{1}{16})-15-\frac{1}{8}=0 \\ 2(x-\frac{1}{4})^2-\frac{121}{8}=0 \\ 2(x-\frac{1}{4})^2=\frac{121}{8} \\ (x-\frac{1}{4})^2=\frac{121}{16} \\ x-\frac{1}{4}=\pm\sqrt{\frac{121}{16}} \\ x-\frac{1}{4}=\pm\frac{11}{4} \\ x=\frac{1}{4}\pm\frac{11}{4}=\frac{1\pm 11}{4} \\ \\ x_1=\frac{1-11}{4}=-\frac{10}{4}=-\frac{5}{2} \\ x_2=\frac{1+11}{4}=\frac{12}{4}=3[/tex]