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2 answers:
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1
Move everything to the left by subtracting 25 from both sides:
Both terms are squares: is the square of
, while 25 is the square of 5. So, we can apply the factoring
To factor the expression as
A multiplication is zero if and only if one of the factors is zero, so we have
2
The discriminant of the quadratic expression is defined as
So, you have
3
Similarly, we have
Answer:
The number of bacteria in the dish after 9.9 minutes is 478
Step-by-step explanation:
The form of the function is , where a is the initial amount (value f(x) at x = 0)
To find a and b let us use two points from the graph and substitute their coordinates in the equation
∵ The graph passes through point (1 , 1)
∴ x = 1 and y = 1
- Substitute them in the equation
∵
∴ a.b = 1 ⇒ (1)
∵ The graph passes through point (1 , 1)
∴ x = 3 and y = 4
- Substitute them in the equation
∵
∴ a.b³ = 4 ⇒ (2)
Use equation (1) to find a in terms of b
∵ a.b = 1
- Divide both sides by b
∴ ⇒ (3)
- Substitute a in equation (2) by equation (3)
∴ . b³ = 4
- Remember the rule
∵ . b³ =
= b²
∴ b² = 4
- Take √ for both sides
∴ b = 2
Substitute the value of b in equation (3) to find a
∵ a =
∴ a = 0.5
∴
∵ f(x) represents the number of bacteria after x minutes
∵ x = 9.9 minutes
- Substitute x by 9.9 to find the number of bacteria
∵
∴ f(9.9) = 477.7128917
- Round it to the nearest whole number
∴ f(9.9) = 478
∴ The number of bacteria in the dish after 9.9 minutes is 478