已知x=9,x-y=-3,则x平方+3xy+y平方等于多少?

因为x=9,x-y=-3
所以y=12
所以x²+3xy+y²=81+3×9×12+144=549

∵x=9
x-y= -3
∴y=x+3=9+3=12
x^2+3xy+y^2
=(x+y)^2+xy
=(x-y)^2+5xy
=(-3)^2+5*9*12
=9+540
=549

y=12，（x-y）平方+5xy=9+5x9x12=549

∵ x = 9 ，x - y = - 3
∴ 9 - y = - 3
- y = - 3 - 9
y = 12
∴ x ² + 3 x y + y ²
= 9 ² + 3 × 9 × 12 + 12 ²
= 81 + 324 + 144
= 81 + 468
= 549

∵x=9,x-y=-3
∴y=12
xy=9*12=108
x平方+3xy+y平方
=x²-2xy+y²+5xy
=(x-y)²+5xy
=(-3)²+5*108
=9+540
=549

解:因为x=9,x-y=-3,所以y=12,所以x^2＋3xy＋y^2=(x-y)^2＋5xy=9＋540=549

由题意得y=12,带入求解式得答案为549