Mathematics: Ineed to pass this class , i don t understand this can someone me ? the focus of the parabola is (3,-7) and the directrix is y= -4 what is an equation of the parabola ? options a) (x -3)^2 = -3(y + 10) b) (x -3)^2 = -1.5(y + 5.5) c) (x -3)^2 = -12(y + 10) d) (x -3)^2 = -6(y + 5.5)

Height=h=8cmRadius=r=4cmWe know NowNew Radius=2(4)=8cmNew Height=2(8)=16cmSo Hence our correct option is Option C...

Ineed to pass this class , i don t understand

marialegarda4211

03.04.2023

Height=h=8cmRadius=r=4cm

We know

$\boxed{\sf \star TSA_{(Cylinder)}=2\pi r(h+r)}$

$\\ \sf\longmapsto TSA_{(Old\:Cylinder)}=2\times \dfrac{22}{7}\times 4(8+4)$

$\\ \sf\longmapsto TSA_{(Old\:Cylinder)}=\dfrac{176}{7}(12)$

$\\ \sf\longmapsto TSA_{(Old\:Cylinder)}=\dfrac{2112}{7}$

$\\ \sf\longmapsto TSA_{(Old\:Cylinder)}=301.7cm^2$

Now

New Radius=2(4)=8cmNew Height=2(8)=16cm

$\\ \sf\longmapsto TSA_{(New\:Cylinder)}=2\times \dfrac{22}{7}\times 8(16+8)$

$\\ \sf\longmapsto TSA_{(New\:Cylinder)}=\dfrac{352}{7}(24)$

$\\ \sf\longmapsto TSA_{(New\:Cylinder)}=\dfrac{8448}{7}$

$\\ \sf\longmapsto TSA_{(New\:Cylinder)}=1204.7cm^2$

$\\ \sf\longmapsto \dfrac{TSA_{(New\:Cylinder)}}{TSA_{(Old\:Cylinder)}}=\dfrac{1204.7}{301.7}$

$\\ \sf\longmapsto \dfrac{TSA_{(New\:Cylinder)}}{TSA_{(Old\:Cylinder)}}=\dfrac{4}{1}$

$\\ \sf\longmapsto\underline{\boxed{\bf{ {TSA_{(New\:Cylinder)}}:{TSA_{(Old\:Cylinder)}}=4:1}}}$

Hence our correct option is Option C

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