
To find: The solution set for the given inequality.

Answer to Problem 42E
Solution set: (−∞,−12)∪[1,∞) .
Explanation of Solution
Given information:
A rational expression is given as - 5+7x1+2x≤4 .
Concept used:
A rational expression has two types of key numbers − zeros and undefined values. Zeros are the values of x for which its numerator is zero. The values of x for which its denominator is zero are its unidentified values. A rational expression changes its signs at its zeros and its unidentified values. A test value is taken from each interval and corresponding value of inequality is calculated (whether positive or negative). The inequality maintains same sign for whole interval.
Calculation:
Given rational expression is - 5+7x1+2x≤4
⇒5+7x1+2x−4≤0⇒5+7x−4−8x1+2x≤0⇒1−x1+2x≤0
To find zeros, put numerator equal to zero,
1−x=0⇒x=1
To find undefined values, put denominator equal to zero,
1+2x=0⇒x=−12
Key numbers are x=−12,1 .
Test interval | Test x− value | Expression value 1−x1+2x≤0 | Conclusion |
(−∞,−12) | x=−1 | 1−(−1)1+2(−1)=−2 | Negative |
(−12,1) | x=0 | 1−(0)1+2(0)=1 | Positive |
(1,∞) | x=6 | 1−(6)1+2(6)=−513 | Negative |
From above table, it can be concluded that inequality is satisfied in the interval (−∞,−12) or [1,∞) .
Hence, solution set for the given inequality will be (−∞,−12)∪[1,∞) .
Graph of the solution set is drawn below.
Chapter 2 Solutions
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