Post a New Question

college algebra

posted by on .

solve the following inequality. write the answer in interval notation
x^3-4x^2-21x<0


please show work so i can understand this problem better! thanks

  • college algebra - ,

    Since x^3-4x^2-21x = x(x+3)(x-7)

    there are no repeated roots. So, at each root, the graph crosses the x-axis, and the function changes sign.

    Starting with large negative x, all 3 factors are negative. So, on the number line, start with - signs and switch at each root:


    ----- -7 +++++ 0 ----- 3 +++++++

    x is in (-oo,-7) U (0,3)

Answer This Question

First Name:
School Subject:
Answer:

Related Questions

More Related Questions

Post a New Question