﹙1﹚x²-9=﹙x-3﹚﹙x+3﹚
﹙2﹚49m²-81n²=﹙7m﹚²-﹙9n﹚²=﹙7m-9n﹚﹙7m+9n﹚
﹙3﹚x²-1/144=1/144﹙144x²-1﹚=1/144﹙12x-1﹚﹙12x+1﹚
﹙4﹚1/9a²-1/25b²=﹙1/3a﹚²-﹙1/5b﹚²=﹙1/3a-1/5b﹚﹙1/3a+1/5b﹚.
﹙1﹚x²-9=﹙x-3﹚﹙x+3﹚
﹙2﹚49m²-81n²=﹙7m﹚²-﹙9n﹚²=﹙7m-9n﹚﹙7m+9n﹚
﹙3﹚x²-1/144=1/144﹙144x²-1﹚=1/144﹙12x-1﹚﹙12x+1﹚
﹙4﹚1/9a²-1/25b²=﹙1/3a﹚²-﹙1/5b﹚²=﹙1/3a-1/5b﹚﹙1/3a+1/5b﹚.