8/9x1/4+9/8x1/4 =(8/9+9/8)x1/4 =〔（8×8+9×9）÷（8×9）〕x1/4 =145/72x1/4 =145/288
8/9x1/4+9/8x1/4=1/4*（8/9+9/8）=1/4*（64/72+81/72）=1/4*145/72=145/288
