SOLUTION: Solve the inequality x(x + 3) > 4. Give your solution in interval notation, using INF for infinity.

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Question 360298: Solve the inequality x(x + 3) > 4. Give your solution in interval notation, using INF for infinity.
Found 2 solutions by robertb, edjones:
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
x%28x%2B3%29%3E4,
x%5E2%2B3x-4%3E0,
%28x-1%29%28x%2B4%29%3E0.
The critical values of the inequality are 1 and -4.
Choose any number less than -4: pick -5. Now %28-5-1%29%2A%28-5%2B4%29%3E0. Therefore (-infinity, -5) is part of the solution set.
Choose any number between -4 and 1: pick 0. Now %280-1%29%2A%280%2B4%29%3C0. Therefore (-4, 1) is not part of the solution set.
Choose any number greater than 1: pick 2. Now %282-1%29%2A%282%2B4%29%3E0. Therefore (1,infinity ) is part of the solution set.
The critical values themselves don't satisfy the original inequality. Therefore the solution set is (-infinity, -5)U(1,infinity).

Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
x(x + 3) > 4
x^2+3x-4=0 First find the zeros.
(x+4)(x-1)=0
x=-4, x=1
Test on either side of these numbers.
x=-5: -5(-5+3)=10>4
x=0: 0<4
X=2: 2(2+3)=10>4
.
(-INF, -4)U(1, INF)
.
Ed