Question

10) If a + b + c = 9 and ab + bc + ca = 15, find :
a2 + b2 + c2.​

Answer 1

Answer:

Hi friend ⭐♥️

$(a + b + c) {}^{2} = 81 \\ squaring \: on \: both \: sides \\ a {}^{2} + b {}^{2} + c {}^{2} + 2(ab + bc + ca) = 81 \\ a {}^{2} + b {}^{2} + c {}^{2} + 2(15) = 81 \\ a {}^{2} + b {}^{2} + c {}^{2} = 51$

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