Question

3. Find the value of 25x2 +36ý2,if(5x+6y)=21 and xy =3,​

Answer 1

Answer:

21=21

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Answer 2

⭐GIVEN:

• 5x+6y=21

• xy=3

⭐TO FIND:

• 25x²+36y²=?

⭐SOLUTION:

METHOD 1:

Now here we use the identity,

( a²+b²) =(a+b) ²-2ab

Here, a=5x and b=6y

So,

(a²+b²) =(a+b) ²-2ab

(25x²+36y²) =(5x+6y) ²-2×5x×6y

(25x²+36y²) =(21) ²-60(3)

(25x²+36y²) =441-180

(25x²+36y²) =261

METHOD 2:

(5x+6y) =21............ (Given)

Squaring on both sides we get,

(5x+6y) ²=(21) ²

→25x²+60xy+36y²=441

→25x²+36y²+60xy=441

→25x²+36y²+60(3) =441

→25x²+36y²+180=441

→25x²+36y²=441-180

→25x²+36y²=261

Therefore, (25x²+36y²) =261