х²-18=0→х²=18→х=√18
х²-0,81=0→х²=0,81→х=√0,81=0,9
16/5х²-45=0→16/5х²=45→х²=45:16/5→х²=225/16→х=√225/16→х=15/4
4/3х²-12=0→4/3х²=12→х²=12:4/3→х²=9→х=√9→х=3
9/5х²-20=0→9/5х²=20→х²=20:9/5→х²=100/9→х=√100/9→х=10/3→х=3 1/3
25/12х²-27=0→25/12х²=27→х²=27:25/12→х²=324/25→х=√324/25→х=18/5→х= 3 3/5