Question

When Luke left his house in the morning, his cell phone battery was partia

charged. Let B represent the charge remaining in Luke's battery, as a perc
hours since Luke left his house. The table below has select values showing t
relationship between t and B. Determine the number of hours until Luke's
dies.

Answer 1

Explanation:

Solution:

From the graph, the coordinates of the points A, B and C are (- 1, 0) (0, - 2) and (2, 0) respectively.

Let the equation representing the graph be y = a * x ^ 2 + bx + c

(1)

The curve represented by (i) passes through A(- 1, 0) B(0, - 2) and C(0, 2) So,

- 2 = 0 + 0 + c

c = - 2

Also 0 = a - b - 2

and 0 = a * (0.4 + 2b - 2)

⇒a a - b = 2 2a + b = 1 (ii) ..(iii)

Adding (ii) and (iii)

3a = 3

a = 1

Substituting the value of a in (ii), we have

1 - b = 2

b = - 1

The equation of the curve is y = a * x ^ 2 + bx + c i.e. y = x ^ 2 - x - 2