Question : If (a + b + c) = 7 and ab + bc + ca = 12, find the value of a2 + b2 + c2.
Option 1: 29
Option 2: 31
Option 3: 27
Option 4: 25
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Correct Answer: 25
Solution : Given: ab + bc + ca = 12 (a + b + c) = 7 Squaring both sides, we get, ⇒ (a + b + c)2 = 72 = 49 ⇒ a2 + b2 + c2 + 2(ab + bc + ca) = 49 ⇒ a2 + b2 + c2 = 49 – 2(ab + bc + ca) ⇒ a2 + b2 + c2 = 49 – (2 × 12) = 49 – 24 = 25 Hence, the correct answer is 25.
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Question : If a + b + c = 1, ab + bc + ca = –1, and abc = –1, then what is the value of a3 + b3 + c3?
Option 1: 1
Option 2: 5
Option 3: 3
Option 4: 2
Question : If a + b + c = 0, then the value of (a + b – c)2 + ( b + c – a)2 + ( c + a – b)2 is:
Option 1: 0
Option 2: 8abc
Option 3: 4(a2 + b2 + c2)
Option 4: 4(ab + bc + ca)
Question : If $a+b+c=5$ and $a^2+b^2+c^2=15$, then find the value of $a^3+b^3+c^3-3 a b c-27$.
Option 1: 23
Option 2: 27
Option 3: 25
Option 4: 21
Question : If p + q = 7 and p2 + q2 = 25, then find the value of pq.
Option 1: 24
Option 2: 12
Option 3: 18
Option 4: 36
Question : For real $a, b, c$ if $a^2+b^2+c^2=ab+bc+ca$, then value of $\frac{a+c}{b}$ is:
Option 2: 2
Option 4: 0
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