After how many hours is the battery power at 75% if the battery decreases by 20% per hour
1 answer:
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Answer:
(-∞, -4] ∪ [5, ∞)
Step-by-step explanation:
Hi!
Alright, so greater (or less) than or equal to is denoted with a bracket.
If x is less than or equal to -4, then the bracket is on the left side.
(___, -4]
Because x is <em>any</em> number under or equal to -4, x can range from negative infinity. However, we use a parentheses for infinity because infinity can never truly be reached.
So, x -4 = (-∞, -4]
X5
Equal to = bracket
X is any number above 5, so
[5, ∞)
Because we want both of these, we use the union sign (∪)
so,
= (-∞, -4] ∪ [5, ∞)