8. 1/4 х^2–0,09=0
1/4 х^2=0,09
х^2=(9•4)/100=0,36
х1=0,6; х2=–0,6
9. 16
---- х^2 – (7у–0,2х)^2 =
25
4 1 4 1
= ( --- х –7у + --- х)( --- х + 7у – --- х) =
5 5 5 5
= (х–7у)(3/5х+7у)
10. 36m^2–1–(6m–1)^2=–8
(6m–1)(6m+1)–(6m–1)^2=–8
(6m–1)(6m+1–6m+1)=–8
2(6m–1)=–8 |:2
6m–1=–4
6m=–3
m=–1/2