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1 answer:
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Answer:
The coordinates of the vertex are (4 , 16)
Step-by-step explanation:
The coordinates of the vertex of a parabola which represents a quadratic equation y = ax² + bx + c are (h , k), where
- h =
- k is the value of y at x = h
∵ The equation of the parabola is y = - x² + 8x
- Compare it by the form of the equation above to find a, b and c
∵ a is the coefficient of x²
∴ a = -1
∵ b is the coefficient of x
∴ b = 8
∵ c is the numerical term
∴ c = 0
The vertex of the parabola is (h , k)
∵ h =
- Substitute the values of a and b
∴ h =
∴ h = 4
∵ k = y at x = h
- Substitute x by 4 and y by k in the equation
∵ k = - (4)² + 8(4)
∴ k = -16 + 32
∴ k = 16
∴ The coordinates of the vertex are (4 , 16)
Answer:
the guarantee period should be less than 136010 miles
Step-by-step explanation:
From the given information;
Let consider Y to be the life of a car engine
with a mean μ = 170000
and a standard deviation σ = 16500
The objective is to determine what should be the guarantee period T if the company wants less than 2% of the engines to fail.
i.e
P(Y < T ) < 0.02
For the variable of z ; we have:
Now;
From Z table ;
At P(Z < -2.06) ≅ 0.0197 which is close to 0.02
Thus; the guarantee period should be less than 136010 miles