Question

What must be subtracted from the sum of 3x²– 3y² + 7 and x² – y² to get 7?​

Answer 1

Step-by-step explanation:

Let z be the quantity being subtracted.

∴−

3

2

x

2

+

2

3

xy+2y

2

−z=3x

2

−2xy−

2

7

y

∴z=−(3x

2

−2xy−

2

7

y)−

3

2

x

2

+

2

3

xy+2y

2

∴z=−

3

11

x

2

+

2

7

xy+2y

2

+

2

7

y

Hence, the quantity to be subtracted is −

3

11

x

2

+

2

7

xy+2y

2

+

2

7

y.

Answer 2

Answer:

$the \: quantity \: to \: be \\ subtracted \: is \:4 {x}^{2} + 4 {y}^{2}$

Step-by-step explanation:

$sum \: of \: 3 {x}^{2} - 3 {y}^{2} + 7 \: and \: {x}^{2} - {y}^{2} \\ (3 {x}^{2} - 3 {y}^{2} + 7) + ( {x}^{2} - {y}^{2} ) \\ 3 {x}^{2} + {x}^{2} - 3 {y}^{2} - {y}^{2} + 7 \\ 4 {x}^{2} - 4 {y}^{2} + 7 \\ let \: z \: be \: the \: no. \: being \: subtracted \\ (4 {x}^{2} - 4 {y}^{2} + 7) -z = 7 \\ - z = 7 - 4 {x}^{2} + 4 {y}^{2} - 7 \\ - z = 7 -7 - 4 {x}^{2} + 4 {y}^{2} \\ - z = - 4 {x}^{2} + 4 {y}^{2} \\ z = 4 {x}^{2} + 4 {y}^{2} \\ hence, \: the \: quantity \: to \: be \\ subtracted \: is \:4 {x}^{2} + 4 {y}^{2}$

$hope \: it \: helps \: you...$