My Math Forum Completely Confused

 Algebra Pre-Algebra and Basic Algebra Math Forum

 July 27th, 2014, 03:45 PM #1 Newbie   Joined: Jul 2014 From: Cohoes, NY Posts: 8 Thanks: 0 Math Focus: NONE!! Completely Confused I don't know how many of these things I can post in a day or even an hour. But this one has me completely confused. -9x(5x + 4) + 10(x + 3) Here is my calculation, which was completely wrong (still working with simplifying equations): -9x(5x + 4) + 10(x + 3) -45x + 36x + 10x + 30 19x + 30 Here was the answer the calculator gave me: -9x(5x + 4) + 10(x + 3) Reorder the terms: -9x(4 + 5x) + 10(x + 3) (4 * -9x + 5x * -9x) + 10(x + 3) (-36x + -45x^2) + 10(x + 3) Reorder the terms: -36x + -45x^2 + 10(3 + x) -36x + -45x^2 + (3 * 10 + x * 10) -36x + -45x^2 + (30 + 10x) Reorder the terms: 30 + -36x + 10x + -45x^2 Combine like terms: -36x + 10x = -26x 30 + -26x + -45x^2 Last edited by lwhitworth67; July 27th, 2014 at 04:00 PM. Reason: wrong calculation
July 27th, 2014, 07:13 PM   #2
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Math Focus: Electrical Engineering Applications
Hi lwhitworth67,

Quote:
 Here is my calculation, which was completely wrong (still working with simplifying equations): -9x(5x + 4) + 10(x + 3) -45x + 36x + 10x + 30
The first two terms should be -45x^2 - 36x. I think you will find that this will lead to the given answer.

July 27th, 2014, 10:48 PM   #3
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Quote:
 Originally Posted by lwhitworth67 -9x(5x + 4) + 10(x + 3) -45x + 36x + 10x + 30 19x + 30
$\displaystyle \ -9x(5x + 4) + 10(x + 3)= \\\;\\ = -45x^2 - 36x + 10x + 30= \\\;\\ = -45x^2 - 26x + 30 .$

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