# intro cal

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the first 3 term of a geometric progression are
k-4, 2k-4, 4k+4.

what is the value of k?

in any geometric progression any term divided by its previous term gives you the common ratio, so ....

(2k-4)/(k-4) = (4k+4)/(2k-4)

cross-multiply and proceed.
I comes out nice, the square term cancels.

how do i cross multiply this?i get confused easiy when doing cross multiply in division...

(2k-4)(2k-4) = (k-4)(4k+4)
4k^2 - 16k + 16 = 4k^2 - 12k - 16
-4k = -32
k=8

ooh so you times it by the opposite!silly me...
Thank you soo much!!

yes, in general

a/b = c/d -----> bc = ad

try it with equivalent fractions

we know 2/3 = 10/15
then 2*15 = 3*10 ...true!

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