SOLUTION: Let x be the numbet of years since 1980 and y be the life expectancy for a person born between ( 1980 + x ) and ( 1980 + x + 5 ). Find the quadratic equation whose graph passess th

Question 1163445: Let x be the numbet of years since 1980 and y be the life expectancy for a person born between ( 1980 + x ) and ( 1980 + x + 5 ). Find the quadratic equation whose graph passess through the points ( 0, 78,2) , ( 5, 79) and ( 10, 79.2 )
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52784)   (Show Source): You can put this solution on YOUR website!
.

This object in parentheses (0,78,2) is not a point in a plane.

==================

To solve the problem successfully, first, you (the visitor) should write the problem correctly.

The second is to FORGET about this wording definition of the function in the first part of the problem,
and concentrate your attention on parabola only.

The first part of the problem's description is a typical "noise", whose destination is to distract
the reader attention and to confuse him.

Do not be amazing : some problems are specially constructed in this way, so you should be ready to it
and should be aware about it.

The rest is just a technique.

/\/\/\/\/\/

The lesson to learn from the solution is THIS :

            In such problems, it is vitally important to separate parts of the description
            that are a "noise", and forget about them.

Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!

Let x be the numbet of years since 1980 and y be the life expectancy for a person born between ( 1980 + x ) and ( 1980 + x + 5 ). Find the quadratic equation whose graph passess through the points (0,78.2), ( 5, 79) and ( 10, 79.2 )

The general quadratic function is

Use the three given data points in that equation to form three equations in the coefficients a, b, and c.

(1)

(2)

(3)

Substitute (1) into (2) and (3) to get two equations in a and b.

(4)
(5)

Subtract (4) from (5).

{6)

Subtract (4) from (6).

(7)

Substitute in (4) to find b.

ANSWER: The quadratic equation is

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