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standard form: terms are written in descending order of exponents from left to right. Leading Coefficient: the coefficient of the variable with the highest degree Degree: the largest exponent on a variable 6.2 Evaluating & Graphing Polynomial Functions Do Now: What is the coefficient? -6x + 5 OBJ: To Evaluate a polynomial function & Graph a polynomial function
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DegreeTypeStandard Form common types of polynomial functions: 4Quartic f (x) = 4x 4 + x 3 - 9x 2 + x + 10 0Constantf (x) = 3 3Cubic f (x) = x 3 - 4x 2 + 6 x - 8 2Quadratic f (x) = -2 x 2 + 4 x + 1 1Linearf (x) = 5x - 2
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Identifying Polynomial Functions Decide whether the function is a polynomial function. If it is, write the function in standard form and state its degree, type and leading coefficient. f (x) = x 2 – 3x 4 – 7 1 2 polynomial function: variable base with whole # exponents degree: 4, so it is a quartic function leading coefficient: – 3 standard form: f(x)=-3x 4 + ½ x 2 - 7 1)
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NOT a polynomial function: because a term does not have a variable base with an exponent that is a whole number. f (x) = x 3 + 3 x 2) f (x) = 6x 2 + 2 x – 1 + x NOT a polynomial function: exponent that is not a whole number. 3)
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f (x) = – 0.5 x + x 2 – 2 Polynomial Function Degree: 2, so it is a quadratic function. Leading coefficient: standard form: f (x) = x 2 – 0.5x – 2. 4) Polynomial function? (DO NOT COPY) f (x) = x 2 – 3 x 4 – 7 1 2 f (x) = x 3 + 3 x f (x) = 6x 2 + 2 x – 1 + x f (x) = – 0.5x + x 2 – 2
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Use synthetic substitution (aka synthetic division) to evaluate: f (x) = 2 x 4 + 8 x 2 + 5 x 7 when x = 3. Using Synthetic Substitution 5)
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Polynomial in standard form 2 x 4 + 0 x 3 + (–8 x 2 ) + 5 x + (–7) 2 6 6 10 18 35 30105 98 The value of f (3) is the last number you write, In the bottom right-hand corner. The value of f (3) is the last number you write, In the bottom right-hand corner. 20–85 –720–85 –7 Coefficients 3 x -value 3 S OLUTION Polynomial in standard form
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Homework
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End Behavior is what happens to f(x) as x gets very large (+ ) or very small (- ) it depends on the degree (odd or even) and the leading coefficient (positive or negative) *The expression x + is read as “x approaches positive infinity.” OBJ: describe the end behavior of a polynomial function DO NOW: complete handout
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END BEHAVIOR FOR POLYNOMIAL FUNCTIONS Even degree: With positive LC: as x + , f(x) + as x - , f(x) + With negative LC: as x + , f(x) - as x - , f(x) - Odd degree: With positive LC: as x + , f(x) + as x - , f(x) - With negative LC: as x + , f(x) - as x - , f(x) +
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1) f (x) = x 3 + x 2 – 4 x – 1 The degree is ODD and the LC is POSITIVE so, as x + , f(x) + and as x - , f(x) - Examples: 2) f (x) = –x 4 – 2x 3 + 2x 2 + 4x The degree is EVEN and the LC is NEGATIVE so, as x + , f(x) - and as x - , f(x) -
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HW:
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x f (x) –3 –7 –2 3 –1 3 0 1 –3 2 3 3 23 S OLUTION To graph the function, make a table of values and plot the corresponding points. Connect the points with a smooth curve and check the end behavior. 1) f (x) = x 3 + x 2 – 4 x – 1 Graphing Polynomial Functions
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x f (x) –3 –21 –2 0 –1 0 0 1 3 2 –16 3 –105 2) Graph f (x) = –x 4 – 2x 3 + 2x 2 + 4x S OLUTION To graph the function, make a table of values and plot the corresponding points. Connect the points with a smooth curve and check the end behavior.
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