x=(a-5)^218x-169=2x-25x=(169-25)/(18-2)=144/16=9a-5=3 or -3a=8 or 2
18(a-5)²-2(a-5)²=169-2516(a-5)²=144(a-5)²=9a-5=3a=8
2和8
2或8
移项16（a-5)²=144，所以（a-5)²=9，所以a-5=3或a-5=-3，即a=8或-2
