SOLUTION: Pls help me to solve this using word problem leading to quadratic equation. This is the question,A girl is 6years younger than her brother.the product of their ages is 135.find the

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Pls help me to solve this using word problem leading to quadratic equation. This is the question,A girl is 6years younger than her brother.the product of their ages is 135.find the      Log On


   

Question 1056543: Pls help me to solve this using word problem leading to quadratic equation. This is the question,A girl is 6years younger than her brother.the product of their ages is 135.find their ages
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = her brother's age
+x+-+6+ = the girl's age
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+x%2A%28+x+-+6+%29+=+135+
+x%5E2+-+6x+=+135+
I will solve by completing the square
+x%5E2+-+6x+%2B+%28-6%2F2%29%5E2+=+135+%2B+%28-6%2F2%29%5E2+
+x%5E2+-+6x+%2B+9+=+135+%2B+9+
+%28+x+-+3+%29%5E2+=+144+
+%28+x+-+3+%29%5E2+=+12%5E2+
+x+-+3+=+12+
+x+=+15+
There is another root you get by taking the
negative square root of +12%5E2+=+-12+,
but ages can't be negative
also:
+x+-+6+=+9+
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The brother is 15
The girl is 9
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check:
+x%2A%28+x+-+6+%29+=+135+
+15%2A9+=+135+
+135+=+135+
OK