Latest TCS Aptitude Question SOLUTION: what is the maximum value of x^3+y^3+3x*y . when x+y = 8 ??

• Placement Papers
• /
• TCS
• /
• Category

TCS Question Papers: TCS Interview Experience(90) TCS Company Profile

(#M40152868) TCS Category question Keep an EYE

what is the maximum value of x^3+y^3+3x*y . when x+y = 8 ??

Asked In TCS luna dutta (8 years ago)

Unsolved Read Solution (5)

Is this Puzzle helpful?   (3)   (1) Submit Your Solution

Read Solution (5) :

akshiya prabhakar  (8 years ago)

As it is not specified that value of x and y are greater than 0 or they can be equal to zero
If we take y as 0 then maximum value will be 512 .
and if both x and y are greater than 0 than maximum value will be 365.

Is this solution Helpfull? Yes (7) | No   

Kunal nemu  (8 years ago)

Answer is 365.
Now x+y=8
so 1+7=8 , xy =7
2+6=8, xy =12
3+5=8, xy = 15
4+4=8, xy =16
If xy =16 then we get the value is 176.
If xy=7..then x=1 and y=7
so x^3+y^3+3 x*y =1^3+7^3+3*1*7 =365..
others two value 197 , 260
so the maximum value 365.

Is this solution Helpfull? Yes (5) | No   

Puja Dhar  (8 years ago)

let x=y=4 and put the values of x and y in the expression i. e
(4^3)+(4^3)+3*4*4=176

Is this solution Helpfull? Yes (1) | No (3)  

ROHIT  (8 years ago)

(x+y)^3= x^3 + y^3 + 3xy(x+y)
so,
(x+y)^3= x^3 + y^3 + 3xy*8 [x+y=8]

(x+y)^3= x^3 + y^3 + 24xy

(x+y)^3 - 21xy= x^3 + y^3 + 3xy

8^3 -21xy=x^3 + y^3 + 3xy

512 -21xy=x^3 + y^3 + 3xy

so the value of x^3 + y^3 + 3xy will be maximum for the minimum value of xy and that is when xy=7.
hence,512- (21*7) =365.

Is this solution Helpfull? Yes (1) | No   

yamini shrivastava  (8 years ago)

given x+y=8
for max the value of x and y must be 4,4
so ans will be 176

Is this solution Helpfull? Yes | No   

Please Login to Read Solution.