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In the following exercises, solve each inequality algebraically and write any solution in interval notation.
-x2+8x-11<0

Short Answer

Expert verified

The solution in interval notation is (-∞,4-5)∪(4+5,∞).

Step by step solution

01

Step 1. Given information.

The given inequality is:
-x2+8x-11<0

02

Step 2. Determine the critical points.

Change the inequality sign to an equal sign and then solve the equation.

-x2+8x-11=0

Use the quadratic formula to solve the equation.

x=-8±(8)2-4(-1)(-11)2(-1)∵x=-b±b2-4ac2ax=-8±20-2x=-8-2±25-2x=4±5

The two critical points 4-5and 4+5divide the number line is three intervals (-∞,4-5),(4-5,4+5),(4+5,∞).

03

Step 3. Determine the intervals where the inequality is correct.

Test point for the interval (-∞,4-5)is x=0.

-(0)2+8(0)-11=-11<0

Test point for the interval (4-5,4+5)is x=3.

-(3)2+8(3)-11=4>0

Test point for the interval (4+5,∞)is x=7.

-(7)2+8(7)-11=-4<0

The inequality -x2+8x-11<0is true over the intervals (-∞,4-5)and (4+5,∞).

04

Step 4. Conclusion.

The solution in interval notation is (-∞,4-5)∪(4+5,∞).

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