a-b+c=7 and a²+b²+c²=19,then what is the value of ca-ab-bc?
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Step-by-step explanation:
(a+b+c)²=a²+b²+c²+2ab+2bc+2ca
a²+b²+c²= (a+b+c)²-2ab-2bc-2ca
a²+b²+c²= (7)²-2(ab+bc+ca) a²+b²+c².
= (7)²-2(20) a²+b²+c²
= 49-40 a²+b²+c²= 9
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