SOLUTION: solve: (2m-9)(6+5m)=(10m+15)(m-2) I am not understanding how to do these!

Algebra ->  Equations -> SOLUTION: solve: (2m-9)(6+5m)=(10m+15)(m-2) I am not understanding how to do these!      Log On


   



Question 585228: solve: (2m-9)(6+5m)=(10m+15)(m-2)
I am not understanding how to do these!

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
All you have to know is this general idea:
+%28+a+%2B+b+%29%2A%28+c+%2B+d+%29+=+a%2Ac+%2B+b%2Ac+%2B+a%2Ad+%2B+b%2Ad+
Practice this:
+8%2A11+=+88+
Now write it this way:
+%28+6+%2B+2+%29%2A%28+7+%2B+4+%29+
Now do what I did above:
+42+%2B+14+%2B+24+%2B+8+
Do the addition:
+42+%2B+14+%2B+24+%2B+8+=+88+
It's the same as +8%2A11+=+88+
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Now do it a little differently
+%28+7+%2B+1+%29%2A%28+3+%2B+8+%29+=+21+%2B+3+%2B+56+%2B+8+
+21+%2B+3+%2B+56+%2B+8+=+88+
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Once you are good at this, you can do
+%28+2m+-+9+%29%2A%28+6+%2B+5m+%29+
+12m+-+54+%2B+10m%5E2+-+45m+
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You can check this. Make +m+=+3+ or any number
+%282%2A3+-+9+%29%2A%28+6+%2B+5%2A3+%29+
+%28+6+-+9+%29%2A%28+6+%2B+15+%29+=+-3%2A21+
+-3%2A21+=+-63+
Now go back to
+%28+2m+-+9+%29%2A%28+6+%2B+5m+%29+=+12m+-+54+%2B+10m%5E2+-+45m+
+12m+-+54+%2B+10m%5E2+-+45m+=+12%2A3+-+54+%2B+10%2A3%5E2+-+45%2A3+
+36+-+54+%2B+90+-+135+
+126+-+189+=+-63+ ( the same answer )
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Just practice, practice, and do this number substitution
to check results
Hope this helps