Question

At z= 12, find the value of 2 - 3( 2² -102).​

Answer 1

Correct option is A)

Given x+y+z=12

Squaring it we get

x2+y2+z2+2(xy+yz+zx)=144

Therefore xy+yz+zx=24

Also 1/x+1/y+1/z=36

Implies (xy+yz+zx)/xyz=36

⇒xyz=(xy+yz+zx)/36=24/36=2/3

We know (x3+y3+z3)=(x+y+z)(x2+y2+z2−xy−yz−zx)+3xyz

⇒x3+y3+z3=(12)(96−24)+2=12∗72+2=866