SOLUTION: Find the coefficient of $y^4$ in the expansion of $(2y - 5)^7.$ My first answer was 70000, but it was incorrect. I'm not sure how to get the right answer.

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Question 1164029: Find the coefficient of $y^4$ in the expansion of $(2y - 5)^7.$
My first answer was 70000, but it was incorrect. I'm not sure how to get the right answer.
Found 2 solutions by solver91311, MathTherapy:
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


You got the wrong because you didn't include the sign. The sign on the coefficient is part of the coefficient.


John

My calculator said it, I believe it, that settles it
Answer by MathTherapy(10555)   (Show Source): You can put this solution on YOUR website!
Find the coefficient of $y^4$ in the expansion of $(2y - 5)^7.$
My first answer was 70000, but it was incorrect. I'm not sure how to get the right answer. 
How did you determine the answer? If you disclose this, someone might be able to tell you where you went wrong, so you don't make that same error in the future! 

FYI: Yes, I agree. 70,000 is WRONG!! 

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