Question 352568
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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