8^x = 15 and 8^y = 25, then 8(2x +y) = ??????
M Marie007 New member Joined Mar 1, 2007 Messages 2 Jul 24, 2007 #1 8^x = 15 and 8^y = 25, then 8(2x +y) = ??????
S Steem New member Joined Oct 11, 2006 Messages 18 Jul 24, 2007 #2 You should use logarithms for this problem. Solve for x and y then substitute them into the final equation. Have you used logarithms before?
You should use logarithms for this problem. Solve for x and y then substitute them into the final equation. Have you used logarithms before?
skeeter Elite Member Joined Dec 15, 2005 Messages 3,216 Jul 24, 2007 #3 since 8<sup>x</sup> = 15 ... 8<sup>2x</sup> = (8<sup>x</sup>)<sup>2</sup> = 15<sup>2</sup>. 8<sup>2x+y</sup> = 8<sup>2x</sup>*8<sup>y</sup> = 15<sup>2</sup>*25
since 8<sup>x</sup> = 15 ... 8<sup>2x</sup> = (8<sup>x</sup>)<sup>2</sup> = 15<sup>2</sup>. 8<sup>2x+y</sup> = 8<sup>2x</sup>*8<sup>y</sup> = 15<sup>2</sup>*25
