How do you solve the inequality $x^2+x-20 >= 0$ ?

Question

The answer key says $-5 <= x <= 4$

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Answer 1 · 2017-09-01T20:42:20

It seems the answer key was for $x^2+x-20 <= 0$ .

The given problem has solution:

$x <= -5$ or $x >= 4$

Given:

$x^2+x-20 >= 0$

This factors as:

$(x+5)(x-4) >= 0$

This will hold if any of the following:

Hence we find the solution set is:

$x in (-oo, -5] uu [4, oo)$

That is:

$x <= -5" "$ or $" "x >= 4$

It seems that the answer key was for a different problem, namely:

$x^2+x-20 <= 0$