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ICSE Class 9 Answered

i f space x to the power of 2 space end exponent plus space y squared plus z to the power of 2 space end exponent equals space 31 space a n d space x plus y plus z space equals space 11 space f i n d space x y plus space y z plus z x space
Asked by siddeshmankar90.9spicertl | 20 May, 2020, 11:11: AM
answered-by-expert Expert Answer
To find xy+yz+zx when given that x2+y2+z2=31 and x+y+z=11
Using the square identity for trinomial, we have
(x+y+z)2 = x2+y2+z2+2(xy+yz+zx) ... (i)
Substituting x2+y2+z2=31 and x+y+z=11 in (i), we have
(11)2 = 31 + 2(xy+yz+zx)
121 = 31 + 2(xy+yz+zx)
2(xy+yz+zx) = 90
xy+yz+zx = 45
Answered by Renu Varma | 20 May, 2020, 07:29: PM

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