Question

If x-y=9 and xy=4 So (x²+y²)=?​

Answer 1

EXPLANATION.

⇒ x - y = 9. - - - - - (1).

⇒ xy = 4. - - - - - (2).

As we know that,

Formula of :

⇒ (x - y)² = x² + y² - 2xy.

Using this formula in the equation, we get.

Put the values in the equation, we get.

⇒ (9)² = x² + y² - 2(4).

⇒ 81 = x² + y² - 8.

⇒ 81 + 8 = x² + y².

⇒ x² + y² = 89.

                                                                                                                     

MORE INFORMATION.

(1) (x + y)² = x² + y² + 2xy.

(2) (x - y)² = x² + y² - 2xy.

(3) (x² - y²) = (x - y)(x + y).

(4) (x² + y²) = (x + y)² - 2xy.

(5) (x³ + y³) = (x + y)(x² - xy + y²).

(6) (x³ - y³) = (x - y)(x² + xy + y²).

(7) (x + y)³ = x³ + 3x²y + 3xy² + y³.

(8) (x - y)³ = x³ - 3x²y + 3xy² - y³.

Answer 2

Answer:

67

Step-by-step explanation:

Squaring both sides, we get,

  (x−y) ²=7²

=>x² +y² −2xy=49

=>x² +y ² −2(9)=49

=>x² +y²   =49+18

=>x² +y²  =67