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Grade 12th pass10 grade maths

Please give the solution for Q.No 17 and 18 with explanation

Question image for Please give the solution for Q.No 17 and 18 with
Profile image of DASARI NAGESWARA RAO
7 Years agoGrade 12th pass
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1 Answer

Profile image of Aditya Gupta
7 Years ago
note that 
3x^2 + 5y^2 + 4z^2 – 4xy – 4xz – 4x – 2y + 25= (x – 2)^2 + (y – 1)^2 + (x – 2y)^2 + (x – 2z)^2 + 20.
for this  expression to b min, all square terms can be made zero.
so x= 2, y= 1, x= 2z or z= 1.
hence minimum value is 20.
kindly approve :)