已知x²-xy=4,xy+y²=-3,求下列各式的值.(1)x²+y² (2)x²+2xy+3y² (3(3)2x²-xy+y²
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已知x²-xy=4,xy+y²=-3,求下列各式的值.(1)x²+y² (2)x²+2xy+3y² (3(3)2x²-xy+y²
已知x²-xy=4,xy+y²=-3,求下列各式的值.(1)x²+y² (2)x²+2xy+3y² (3
(3)2x²-xy+y²
已知x²-xy=4,xy+y²=-3,求下列各式的值.(1)x²+y² (2)x²+2xy+3y² (3(3)2x²-xy+y²
1)
x²+y²
=(x²-xy)+(xy+y²)
=4+(-3)
=1
2)
x²+2xy+3y²
=(x²-xy)+3(xy+y²)
=4+3×(-3)
=4-9
=-5
1) 1
2) -5
3)
(1) 1 1式+2式
(2) -5 1式+2式乘3
(3) 5 1式乘2+2式
1、x²+y² =4-3=1
2、xy+y²=-3 2(xy+y²)=-6 。x²+2xy+3y² =-6+1=-5
(1)x²+y²=x²-xy+xy+y²
=4+(-3)=1
(2)x²+2xy+3Y²=x²-xy+3(xy+y²)
=4+3(-3)=-5
1、1
2、-5
(1) 1 式1+式2
(2) -5 式1+式2乘3
(3)5 式1乘2+式2