DLA Discovery guide

Discovery guide 3.1 Discovery guide
A4 US

In this set of discovery activities, we look at some places where linear systems naturally arise.

Discovery 3.1.

Use the Law of Conservation (in this case, flow in equals flow out at each point of intersection) in the flow network below to set up a system of equations to determine the internal flow rates. (Do not solve your system.)

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A flow network.

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Discovery 3.2.

Set up a system of equations to balance the chemical equation:

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a {NH}_{3} + b O_{2} \to c NO + d H_{2} O .

Do not solve your system.

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Discovery 3.3.

Any two (distinct) points in the Cartesian plane determine a unique line. Set up a system of equations that would let you solve for the slope and

y

-intercept of the line

y = m x + b

that passes through the points

(- 3, 4)

and

(2, - 1)

(but do not solve the system). Write down the augmented matrix for your system.

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Discovery 3.4.

Any three (distinct, noncollinear) points in the Cartesian plane determine a unique parabola. Set up a system of equations that would let you solve for the coefficients

a, b, c

of the parabola

y = a x^{2} + b x + c

that passes through the points

(- 1, - 4),

(1, 0),

and

(2, 5)

(but do not solve the system). Write down the augmented matrix for your system.

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Discovery 3.5.

Based on the previous two activities and their answers, how many points are necessary to determine a unique degree

n

polynomial

y = a_{n} x^{n} + a_{n - 1} x^{n - 1} + \dots + a_{1} x + a_{0} ?

If you knew such points

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(x_{1}, y_{1}), (x_{2}, y_{2}), (x_{3}, y_{3}), \dots,

and you used these points to create a linear system to determine the coefficients of the polynomial, what would be the pattern in the rows of the resulting augmented matrix for the system?

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