SOLUTION: Please help with this problem. I'm supposed the simplify the equation 5(2y-z)2+4(y+2z)2. The answer I keep getting is 28y + 6z. My textbook has the answer as 24y2-4yz+21z2. How did

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Question 352568: Please help with this problem. I'm supposed the simplify the equation 5(2y-z)2+4(y+2z)2. The answer I keep getting is 28y + 6z. My textbook has the answer as 24y2-4yz+21z2. How did the text book come up with this answer?
Found 2 solutions by stanbon, Waveez:
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
I'm supposed the simplify the equation 5(2y-z)^2+4(y+2z)^2.
The answer I keep getting is 28y + 6z.
My textbook has the answer as 24y2-4yz+21z2.
How did the text book come up with this answer?
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5(2y-z)^2+4(y+2z)^2
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= 5[4y^2-4yz+z^2) + 4(y^2+4yz+4z^2)
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= 20y^2-20yz+5z^2 + 4y^2+16yz+16z^2
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= 24y^2 -4yz + 21z^2
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Cheers,
Stan H.
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Answer by Waveez(3) (Show Source):
You can put this solution on YOUR website!
5(2y-Z)^2 + 4(y+2Z)^2
= 5 [ 4y^2 + 4Zy + Z^2 ] + 4 [ y^2 + 4Zy + 4Z^2 ]
= 20y^2 + 20Zy + 5Z^2 + 4y^2 + 16Zy + 16Z^2
= 20y^2 + 4y^2 - 20Zy +16Zy + 5Z^2 + 16Z^2
= 24y^2 - 4Zy + 21Z^2
Perhaps you had did some careless mistakes in the process.