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there
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Question 5 of 20
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The polynomial equation <u>x³ - 4x² - 7x + 28 = 0</u>, has solutions <u>-√7, √7,</u> and <u>4</u>, among which <u>√7</u> and <u>4</u> are positive real solutions. Hence we have two positive real solutions. Hence, <u>option D</u> is the right choice.
In the question, we are asked for the number of positive real solutions for the polynomial equation, x³ - 4x² - 7x + 28 = 0.
To find the solutions, we do as follows:
x³ - 4x² - 7x + 28 = 0,
or, (x³ - 7x) - (4x² + 28) = 0 {Grouping},
or, x(x² - 7) - 4(x² - 7) = 0 {Taking common},
or, (x - 4)(x² - 7) = 0 {Grouping},
or, (x - 4)(x + √7)(x - √7) = 0 {Using the formula: }.
By the zero-product rule, the solutions are:
x - 4 = 0, or, x = 4,
x + √7 = 0, or, x = -√7,
x - √7 = 0, or, x = √7.
Thus, the positive real solutions are 4, and √7. Hence, there are two positive real solutions.
Thus, the polynomial equation <u>x³ - 4x² - 7x + 28 = 0</u>, has solutions <u>-√7, √7,</u> and <u>4</u>, among which <u>√7</u> and <u>4</u> are positive real solutions. Hence we have two positive real solutions. Hence, <u>option D</u> is the right choice.
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The complete question is:
"Which of the following expresses the possible number of positive real solutions for the polynomial equation shown below?
x³-4x²-7x+28=0
a. two or zero
b. three or one
c. one
d. two"