Question

Question 17 Find the equation for the ellipse that satisfies the given conditions: Foci (±3, 0), a = 4

Class X1 - Maths -Conic Sections Page 255

Answer 1

concept : for foci( ±c, 0) where , c² = a² - b² , equation of ellipse will be of the form , x²/a² + y²/b² = 1

Given,
Foci ( ± 3 , 0) = ( ± c , 0)
hence, c = 3 and given a = 4
so, c² = a² - b²
3² = 4² - b²
3² - 4² = - b²
b² = 4² - 3² = 16 - 9 = 7

hence, equation of ellipse
x²/a² + y²/b² = 1
put a² = 16 , b² = 7
x²/16 + y²/7 = 1

Answer 2

Hii friend,

For ellipse
Focus (+_c,0)

:-c=3 a= 4

a²-b²= c².
16-b²= 9

b²=7

For ellipse,

x²/a²+y²/b²= 1

x²/16+y²/7=1

Hope this helps you a little!!