(x^2/4)+(y^2/49)=1
б)
2b=10
b=5
c=4
a^2=b^2-c^2=5^2-4^2=9
(x^2/9)+(y^2/25)=1
в)
с=12
ε =с/b
ε =12/13 ⇒ b=13
a^2=b^2-c^2=13^2-12^2=25
(x^2/25)+(y^2/169)=1
г)
2a=8
a=4
ε =4/5
ε =с/b
с/b=4/5 ⇒ c=(4/5)b
a^2=b^2-c^2=b^2-((4/5)b)^2=(9/25)b^2
a^2=16
9/25b^2=16
b^2=16*25/9=400/9
(x^2/16)+(y^2/(400/9))=1
д)