Question

help needed
http://prntscr.com/zbsbi
i got the answer x = 8.78 , 108.78

Answer 1

x = 8.78 , -108.78

Answer 2

i calculate it but can you solve it for me so i can compare my method

Answer 3

what is the question? You found the radius of the vase. It is r= 8.78

Answer 4

btw, in your print screen, the line that reads
100 pi r + pi r^2 = 300 should read

100 pi r + pi r^2 = **3000**

Answer 5

Your answer 8.78 is the correct radius. Discard the negative one.

Answer 6

ok but what about 3000
100 pi r + pi r^2 = 3000
is this quadratic equation right

Answer 7

yes, that equation comes from what they told you about the surface area of the cylinder

Answer 8

This gives the details on how to find the surface area
http://www.basic-mathematics.com/surface-area-of-a-cylinder.html

Answer 9

\[r^2 + 100r - 3000 / \pi = 0\]

Answer 10

and is this equation right

Answer 11

yes

Answer 12

you can re-arrange
100 pi r + pi r^2 = 3000
to
pi r^2 +100 pi r -3000 =0

now divide both sides of the equation (all terms) by pi
pi r^2/pi + 100 pi r/pi -3000/pi =0

the pi/pi 's cancel out (i.e pi/pi = 1 )
you get
r^2 +100 r -3000/pi=0

Answer 13

thanks can you help with another question i'll make another post

Answer 14

I should have written
pi r^2/pi + 100 pi r/pi -3000/pi =0/pi
and also said that 0/pi is still 0, so you get

r^2 +100 r -3000/pi=0