Question : If $a + b + c = 6$ and $a^2+b^2+c^2=40$, then what is the value of $a^3+b^3+c^3-3abc$?
Option 1: 212
Option 2: 252
Option 3: 232
Option 4: 206
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Correct Answer: 252
Solution : Given that $a + b + c = 6$ and $a^2+b^2+c^2=40$, $(a+b+c)^2 = a^2 + b^2 + c^2 + 2(ab+bc+ac)$. $⇒6^2 = 40 + 2(ab+bc+ac)$ $⇒ab+bc+ac = -2$ $a^3+b^3+c^3-3abc=(a+b+c)(a^2+b^2+c^2-ab-bc-ac)$ $⇒a^3+b^3+c^3-3abc=6 \times (40 +2)$ $⇒a^3+b^3+c^3-3abc=6 \times 42 $ $⇒a^3+b^3+c^3-3abc=252 $ Hence, the correct answer is 252.
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Question : If $9 a+9 b+9 c=81$ and $4 a b+4 b c+4 c a=160$, then what is the value of $6 a^2+6 b^2+6 c^2$?
Option 1: 1
Option 2: 3
Option 3: 4
Option 4: 6
Question : If $(a+b+c) \neq 0$, then $(a+b+c)\left(a^2+b^2+c^2-a b-b c-c a\right)$ is equal to:
Option 1: $a^3+b^3-c^3-3abc$
Option 2: $a^3-b^3+c^3-3abc$
Option 3: $a^3+b^3+c^3-3abc$
Option 4: $a^3+b^3+c^3+3abc$
Question : If $a+b+c=0$ and $a^2+b^2+c^2=40$, then what is the value of $a b+b c+c a$?
Option 1: –30
Option 2: –20
Option 3: –25
Option 4: –40
Question : If $a + b + c = 12$ and $ab + bc + ca = 22$, then what is the value of $a^3 + b^3 + c^3 - 3abc ?$
Option 1: 1052
Option 2: 936
Option 3: 924
Option 4: 876
Question : What is the value of (a + b + c) {(a - b)2 + (b - c)2 + (c - a)2}?
Option 1: $2 a^3+2 b^3+2 c^3$
Option 2: $2a^3+2b^3+2c^3-6abc$
Option 3: $3abc$
Option 4: $6abc$
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