Question

Plz solve the 20th question I am not able to understand the question itself .

Answer 1

According to the question,

8x³ + 27y³ = 730 ---------- equation (i)

3x² + 3y² = 15 -----------equation (ii)

We have to find the value of (2x + 3y)

Let us see what will be the cube of (2x + 3y)

i.e. (2x + 3y)³ = 8x³ + 3x²y + 3xy² + 27y³

or, we can also group it as: (8x³ + 27y³) + (3x²y + 3xy²)

Now, we have the value of this expressions,

(8x³ + 27y³) + (3x²y + 3xy²) = 730 + 15 = 745

But, it is not the answer, because we are bothered of (2x + 3y)³ and not (2x + 3y).

Therefore, if we do the cube root of it then we can get the value of (2x + 3y).

Therefore, (2x + 3y) = cube root of (2x + 3y)³ = cube root of 745 = 9.065 (Ans)

Answer 2

Your question seems to be incorrect. It should be 2x^2y + 2xy^2 = 15.

Given Equation is 8x^3 + 27y^3 = 730 ------- (1)

Given Equation is 2x^2y + 3xy^2 = 15 -------- (2)

Now,

On cubing, we get

= > (2x + 3y)^3

= > 8x^3 + 27y^3 + 3(2x)^2(3y) + 3(2x)(3y)^2

= > 8x^3 + 27y^3 + 36x^2y + 54xy^2

= > 8x^3 + 27y^3 + 18(2x^2y + 3xy^2)

= > 730 + 18(15)

= > 730 + 270

= > 1000.

Hence,

= > (2x + 3y)^3 = 1000

= > 2x + 3y = 10.

Therefore, the value of (2x + 3y) = 10.

Hope this helps!