已知a-b=2,a-c=½,求a方+b方+c方-ab-ac-bc

已知a-b=2,a-c=½,求a方+b方+c方-ab-ac-bc
已知a-b=2,a-c=½,求a方+b方+c方-ab-ac-bc

已知a-b=2,a-c=½,求a方+b方+c方-ab-ac-bc
∵a-b=2,a-c=½,∴两式相减得：c-b=3/2
原式=½{2a²+2b²+2c²-2ab-2ac-2bc}
=½{（a-b)²+(a-c)²+(b-c)²}
=½{（4+1/4+9/4}
=3.25
∞ ①②③④⑤√ λμξ⊙°³π²αβγφθ∵∴