SOLUTION: Suppose f(x) = (x-7)(x+4). (a) For which values of x is the function f(x) positive? Enter your answer using inequalities. help (inequalities) (B) For which values of x i

Question 924062: Suppose f(x) = (x-7)(x+4).
(a) For which values of x is the function f(x) positive? Enter your answer using inequalities.
help (inequalities)
(B) For which values of x is the function f(x) negative? Enter your answer using inequalities.
help (inequalities)
need part b please already got part a
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
find the points where the value is equal to 0.
that would be at x = 7 and x = -4
now look at the intervals that are created.
there will be 3.
first interval is when x is smaller than -4
second interval is when x is between -4 and 7
third interval is when x is greater than 7.

now pick a point in each interval and evaluate the expression.

when x = -5, (-5-7)(-5+4) = -12*-1 = 12 = positive.
when x = 0, (0-7)(0+4) = -7*4 = -28 = negative.
when x = 10, (10-7)(10+4) = 3*14 = 42 = positive

the function is positive when x < -4 or x > 7

the function is negative when x > -4 and x < 7 which can be written as 4 < x < 7

the function is zero when x is = -4 or x = 7

the graph of the function is shown below:

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