Answer:
x=9
x=-1
Step-by-step explanation:
1.x²-8x-9=0
2.(x-4)²-9-4²=0
3.(x-4)²=9+4²
4.(x-4)²=9+4²
5.(x-4)²=9+16
6.(x-4)²=25
7.x-4=¥√25
8.x=¥15+4
9.x=4+5
x=4-5
10.x=9
