x²+y²=(x+y)²-2xy=9²-2*16=81-32=49x²+y²-4xy=(x+y)²-2xy-4xy=(x+y)²-6xy=9²-6*16=81-96=-15
x²+y²=(x+y)²-2xy =81-32=49x²+y²-4xy=(x+y)²-6xy =81-96= -15
