# Regents Review #3 Functions Quadratics & More.

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Regents Review #3 Functions Quadratics & More

Quadratic Functions The graph of a quadratic function is a U-shaped curve called a parabola. The vertex (turning point) is the lowest point (minimum point) of the parabola when it opens up and the highest point (maximum point) when it opens down.

Quadratic Functions How do we graph quadratic functions in standard form? Standard Form: y = ax2 + bx + c Find the coordinates of the vertex Create a table of values (vertex in the middle) Graph the function (parabola) Label the graph with the equation

Quadratic Functions Graph y = x2 + 4x + 3
Finding the coordinates of the vertex and the axis of symmetry Finding the x-coordinate y = x2 + 4x + 3 a = 1, b = 4 x = Finding the y-coordinate y = x2 + 4x + 3 y = (-2)2 + 4(-2) + 3 y = 4 – 8 + 3 y = -1 x = x = -2 Vertex = (-2, -1)

Quadratic Functions Axis of Symmetry x = -2 -3 -2 -1
Domain: {x | x is all Real Numbers} Range: {y | y > -1} y= x2 + 4x + 3 x y -5 8 -4 3 -3 -2 -1 1 x-intercept (-3, 0) Root: -3 x-intercept (-1, 0) Root: -1 Vertex

Quadratic Functions The roots (zeros) of a quadratic function are the x-values of the x-intercepts. Root: -1 1 Roots (2 equal roots) 2 Roots No real roots Root: 3

Quadratic Functions We can identify the “roots” of a quadratic function by looking at the graph of a parabola. We can also identify the roots algebraically. Consider the graph of y = x2 + x – 6 Set y equal to zero and solve for x. x-intercept: (x, 0) 0 = x2 + x – 6 0 = (x + 3)(x – 2) x + 3 = 0 x – 2 = 0 x = x = 2 The function expressed in factored form is y = (x + 3)(x – 2) The roots are {-3, 2}

Quadratic Functions How does a affect the graph of y = ax2 + bx + c ?
As the |a| increases, the graph becomes more narrow As |a| decreases, the graph becomes wider  If a > o, the parabola opens up If a < 0, the parabola opens down

Quadratic Functions Rewrite the function f(x) = x2 – 4x + 5 in vertex form by completing the square and identify the vertex of the function. f(x) = x2 – 4x + 5 y = x2 – 4x + 5 opens up or down (a value) y-intercept (c value) y – 5 = x2 – 4x y – = x2 – 4x + 4 (x – 2)(x – 2) y – 1 = (x – 2) 2 y = (x – 2) f(x) = (x – 2) Vertex: (2, 1) opens up or down (a value) Vertex (h, k)

Quadratic Functions Parabolic Functions Increase and Decrease
The function is decreasing when x < 2. The function is increasing when x > 2. The function does not increase or decrease at 2. The function is increasing when x < 1. The function is decreasing when x > 1. The function does not increase or decrease at 1.

Opens up Minimum point x approaches + ∞ and - ∞ ends (y –values) approach + ∞ Opens down Maximum point ends (y-values) approach - ∞ x y 4 2 x y -1 1 2

Quadratic Functions A – Find the Vertex B – between 3 and 4 seconds
An angry bird is launched 80 feet above the ground and follows a path that can be modeled by the function h(t) = -16t2 + 64t + 80 where h(t) represents the birds height after t seconds. How long will it take the bird to reach its maximum height? What is the maximum height the bird will reach? Approximately, how long will it take the bird to hit a target 100 feet above the ground (see graph)? If the bird misses the target, at what time will it hit the ground? A – Find the Vertex t time h(t) height 80 1 128 2 144 3 4 5 B – between 3 and 4 seconds C – The bird will hit the ground at 5 seconds. h(2) = -16(2) (2) + 80 h(2) = 144 Algebraic Approach Replace h(t) with the given height and solve for t B = -16t2 + 64t + 80 C = -16t2 + 64t + 80 Vertex: (2, 144) It will take 2 seconds for the bird to reach its maximum height of 144 feet.

Quadratic Functions Algebraic Approach (letters B and C on the previous slide) B. Approximately, how long will it take the bird to hit a target 100 feet above the ground (see graph)? Looking at where the target is located, the bird would have hit the target on its descend (past the vertex) which means the bird would have taken about 3.66 seconds to hit the target located 100 feet above the ground. C. If the bird misses the target, at what time will it hit the ground? The bird will hit the ground when h(t) = 0 (height = 0 ft). This happens at 5 seconds. We reject -1 because we cannot have negative time.

Absolute Value Functions
y = |x| x y -2 2 -1 1 Vertex: (0,0) Domain: {x|x is all Real Numbers} Range: {y|y > 0} Function decreases when x < 0 Function increases when x > 0 End Behavior: as x approaches + ∞ and -∞, the ends approach + ∞ Reminder: The graph does not increase or decrease at the vertex Characteristics of

Absolute Value Functions
The function becomes more narrow (x 2) Parent Function Vertex: (3, -4) The function shifts 3 units right The function moves 4 units down

Square Root Functions x y 1 4 2 9 3
Domain: {x| x > 0} Range: {y| y > 0} x y 1 4 2 9 3 The domain is restricted because you cannot take the square root of a negative number.

Square Root Functions Parent Function Domain: {x| x > 0}
Range: {y| y > 0} Shifts 1 unit right Domain: {x| x > 1} Range: {y| y > 0} Shifts 2 units up Domain: {x| x > 1} Range: {y| y > 2}

Cubic Functions Domain: {x | x is all Real Numbers}
y -2 -8 -1 1 2 8 Domain: {x | x is all Real Numbers} Range: {y | y is all Real Numbers} End Behavior: As x approaches – ∞, the ends of the graph approach – ∞ As x approaches + ∞, the ends of the graph approach + ∞

Cube Root Functions Domain: {x | x is all Real Numbers}
y -8 -2 -1 1 8 2 Domain: {x | x is all Real Numbers} Range: {y | y is all Real Numbers} End Behavior: As x approaches – ∞, the ends of the graph approach – ∞ As x approaches + ∞, the ends of the graph approach + ∞

Piecewise Functions A piecewise function has different rules (equations) for different parts of the domain. x + 3 x2 3 x y -1 2 -2 1 -3 -4 x y -1 1 2 4 x y 2 3 4 5 x2 3 x + 3 Evaluate f (1.5) f(x) = x2 f(1.5) = (1.5)2 = 2.25

Piecewise Functions A STEP FUNCTION is a piecewise function that is discontinuous and constant over a finite number of intervals. How much does it cost to mail a letter weighing 3 ½ ounces? 45 cents Jan says that it costs 43 cents to mail a letter weighing 2 ounces. Do you agree or disagree with Jan? Disagree. The point (2, 43) graphed with an open circle tells us that 2 oz. does not cost 43 cents. The closed circle above 2 shows us that the cost of 2 oz. is 41 cents.

Piecewise Functions A wholesale t-shirt manufacturer charges the following prices for t-shirt orders: \$20 per shirt for shirt orders up to 20 shirts. \$15 per shirt for shirt between 21 and 40 shirts. \$10 per shirt for shirt orders between 41 and 80 shirts. \$5 per shirt for shirt orders over 80 shirts. Create a graph that models this situation. You've ordered 40 shirts and must pay shipping fees of \$10. How much is your total order? Solution If 40 shirts are ordered, each shirt will cost \$15. (40 shirts x \$15) + \$10 shipping = \$610