Question

what should be taken away from 3x² - 4y²+ 5xy +20 to obtain -x² - y²+XY + 20 ?​

Answer 1

Answer:

Let the number substacted be a

Then

3x²-4y²+5xy+20-a= -x²-y²+6xy+20

3x²+x²-4y²+y²+5xy-6xy+20-20=a

4x²-3y²-xy=a

Then the number which should taken away is 4x²-3y²-xy

Step-by-step explanation:

Answer 2

Answer:

$4x^2+4xy-3y^2$

Step-by-step explanation:

$A=3x^2 - 4y^2+ 5xy +20\\B=-x^2 - y^2+xy + 20$

C should be taken away from A to obtain B

$A-C=B$

We want C

∴$C=A-B$

∴$C=4x^2+4xy-3y^2$