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ꯀꯔꯤꯒꯨꯝꯕꯥ $a + b + c = 6$ ꯑꯃꯁꯨꯡ $a^2 + b^2 + c^2 = 14$ ꯑꯣꯏꯔꯕꯗꯤ, $ab + bc + ca$ ꯊꯤꯌꯨ꯫

A$11$
B$13$
C$10$
D$9$
Answer & Solution
Correct answer: A. $11$
$(a+b+c)^2=a^2+b^2+c^2+2(ab+bc+ca)$ ꯁꯤꯖꯤꯟꯅꯕꯅꯥ $36=14+2(ab+bc+ca)$ ꯄꯤ꯫ ꯃꯔꯝ ꯑꯗꯨꯅꯥ $ab+bc+ca=(36-14)/2=11$, ꯃꯔꯝ ꯑꯗꯨꯅꯥ ꯑꯣꯄꯁꯟ A ꯑꯁꯤ ꯑꯆꯨꯝꯕꯅꯤ꯫ ꯀ꯭ꯔꯣꯁ-ꯄ꯭ꯔꯗꯛꯇ ꯁꯣꯝ ꯑꯁꯤ $2$ꯅꯥ ꯃꯜꯇꯤꯄꯜ ꯇꯧꯏ, ꯃꯔꯝ ꯑꯗꯨꯅꯥ ꯈꯦꯠꯅꯕꯥ $22$ ꯑꯁꯤ $2$ꯅꯥ ꯈꯥꯌꯗꯣꯀꯄꯥ ꯇꯥꯏ꯫
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