Answer:
19
Explanation:
[tex](a + b + c)^{2} \\= a^2 +b^2+c^2 + 2ab + 2bc + 2ca \\ \\ (a + b + c)^{2} \\ = a^2 +b^2+c^2 + 2(ab + bc + ca) \\ \\ (7) ^{2} = a^2 +b^2+c^2 + 2(15) \\ \\ 49 = a^2 +b^2+c^2 + 30 \\ \\ a^2 +b^2+c^2 = 49 - 30 \\ \\ \huge \red{a^2 +b^2+c^2} \blue{= } \purple{19} \\ \\ [/tex]
