a swimmer swam 48 kilometers in d days. What is the value of the d if the swimmer swam an average of 3.2 kilometers daily?
1 answer:
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Answer:
<h2>c. x = -4 or x = 9</h2>Step-by-step explanation:
Domain:
solution:
use <em>(a - b)(a + b) = a² - b²</em>
multiply both sides by (x - 3) ≠ 0
cancel (x - 3)
subtract from both sides
cross multiply
use FOIL
subtract 4x from both sides
combine like terms
change the signs
The product is 0 if one of the factors is 0. Therefore:
<em>add 9 to both sides</em>
<em>subtract 4 from both sides</em>
Answer:
C
Step-by-step explanation:
Calculate AC using Pythagoras' identity in ΔABC
AC² = 20² - 12² = 400 - 144 = 256, hence
AC = = 16
Now find AD² from ΔACD and ΔABD
ΔACD → AD² = 16² - (20 - x)² = 256 - 400 + 40x - x²
ΔABD → AD² = 12² - x² = 144 - x²
Equate both equations for AD², hence
256 - 400 + 40x - x² = 144 - x²
-144 + 40x - x² = 144 - x² ( add x² to both sides )
- 144 + 40x = 144 ( add 144 to both sides )
40x = 288 ( divide both sides by 40 )
x = 7.2 → C