2x-6 per x+3 + 6 per x-3 =

2x-6/x+3 + 6/x-3
= (2x²-12x+18)+(6x+18)/x²-9
= 2x²-12x+6x+18+18/x²-9
= 2x²-6x+36/x²-9

tanpa tanda kurung, perhitungan mengikuti aturan urutan operasi

2x-6 / x+3 + 6 / x-3
= 2x - 6/x + 3 + 6/x - 3
= 2x ← jawaban

cek
http://m.wolframalpha.com/input/?i=2x-6+%2F+x%2B3+%2B+6+%2F+x-3&x=8&y=8