Math, asked by akshatgarg67, 1 year ago

if x-y=5 and xy=84 find the value of x cube - y cube​

Answers

Answered by muskantamrakar26
2

Answer:

Answer is 1385.

Explanation step by step:

we know that,

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

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

=> x^3 - y^3 = (x - y)^3 + 3xy (x - y) => x^3 - y^3 = (5)^3 + 3 (84) (5)

=> x^3 - y^3 = (x - y)^3 + 3xy (x - y) => x^3 - y^3 = (5)^3 + 3 (84) (5) => x^3 - y^3 = 125 + 1260

=> x^3 - y^3 = (x - y)^3 + 3xy (x - y) => x^3 - y^3 = (5)^3 + 3 (84) (5) => x^3 - y^3 = 125 + 1260= 1385

Answered by dhmakaqueen
4

Answer:

Hey mate here is ur ans...

 {x}^{3}  -  {y}^{3}  = 1385

Step-by-step explanation:

Given,

x - y = 5..........(1) \\ xy = 84.............(2) \\ squaring \: (1) \: we \: get \\{ (x - y)}^{2}  =  {5}^{2} \\  {x}^{2}   +  {y}^{2}  - 2(xy) = 25 \: (using(2)) \\  {x}^{2}  +  {y}^{2}  - 2(84) = 25 \\  {x }^{2}  +  {y}^{2}  - 168 = 25 \\  {x}^{2}  +  {y}^{2}  = 25 + 168 \\  {x}^{2}  +  {y}^{2}  = 193 ........(3) \\ now \\  {x}^{3}  -  {y}^{3}  = (x - y)( {x}^{2}  + xy +  {y}^{2} ) \\  = (5)(193+84) \\  = 1385

Hope this helps u

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