SOLUTION: x(x+3)= 18

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Question 294621: x(x+3)= 18
Answer by Monkibat(7) About Me  (Show Source):
You can put this solution on YOUR website!
First distribute the x to (x+3). x%28x%2B3%29, x times x = x%5E2 and x times 3 = 3x. Now we have x%5E2%2B3x=18. Now set the equation to zero by subtracting both sides by 18. Now we have the equation: x%5E2%2B3x-18=0. Now we can factor the equation. We have to find factors of -18 that add to +3. Positive 6 and negative 3 are factors that work. x%5E2%2B3x-18=0 factors to %28x%2B6%29%28x-3%29=0. Now set each equation to zero and solve. x%2B6=0, subtract 6 from both sides, x=-6. Now x-3=0, add 3 to both sides, x=3. The answers are x=-6 and x=3. We're not done, we have to check to make sure both solutions work. Plug -6 into the original equation x%28x%2B3%29=18, -6%28-6%2B3%29=18=-6%28-3%29=18=18=18. Therefore x=-6 works and is one of your answers, now we have to check x=3 by plugging 3 into the original equation. 3%283%2B3%29=18=3%286%29=18=18=18. Therefore x=3 works and is one of the solutions too. -6 and 3 are you answers.