SOLUTION: x varies directly as the square of s and inversely as t. How does x change when s is doubled? When both s and t are doubled?

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Question 213783This question is from textbook Structure and Method Book 1
: x varies directly as the square of s and inversely as t. How does x change when s is doubled? When both s and t are doubled? This question is from textbook Structure and Method Book 1

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
This can be expressed as:
x+=+ks%5E2%2Ft where k is the contant of variation.
To find out what happens to x when s is doubled, substitute s = 2s.
x+=+k%282s%29%5E2%2Ft
x+=+4ks%5E2%2Ft Substitute ks%5E2%2Ft+=+x
x+=+4x
X quadruples when s is doubled.
TO find out what happens to x when both s and t are doubled, substitute s = 2s and t = 2t.
x+=+ks%5E2%2Ft
x+=+k%282s%29%5E2%2F2t
x+=+4ks%5E2%2F2t
x+=+2ks%5E2%2Ft Substitute ks%5E2%2Ft+=+x
x+=+2x
x is doubled when both s and t are doubled.