Question : If $a+b+c=7$ and $a^3+b^3+c^3-3abc=175$, then what is the value of $(a b+b c+c a)$?
Option 1: 8
Option 2: 9
Option 3: 7
Option 4: 6
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Correct Answer: 8
Solution : The given equations are: $a + b + c = 7$ $a^3 + b^3 + c^3 - 3abc = 175$ From the identity, $a^3 + b^3 + c^3 - 3abc = (a + b + c)[( a + b + c)^2-3(ab + bc + ca)]$ $⇒175 = 7[( 7)^2-3(ab + bc + ca)]$ $⇒25 = 49-3(ab + bc + ca)$ $⇒24 = 3(ab + bc + ca)$ $⇒(ab + bc + ca)=8$ Hence, the correct answer is 8.
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Question : If $a+b+c=6$ and $a^2+b^2+c^2=14$, then what is the value of $(a-b)^2+(b-c)^2+(c-$ a) ${ }^2$?
Option 1: –8
Option 2: 8
Option 3: 10
Question : What is the value of ${a}^3+{b}^3+{c}^3$ if $(a+b+c)=0$?
Option 1: $a^2+b^2+c^2-3abc$
Option 2: $0$
Option 3: $3abc$
Option 4: $a^2+b^2+c^2-ab-bc-ca$
Question : If $\frac{(a+b)}{c}=\frac{6}{5}$ and $\frac{(b+c)}{a}=\frac{9}{2}$, then what is the value of $\frac{(a+c)}{b}\; ?$
Option 1: $\frac{9}{5}$
Option 2: $\frac{11}{7}$
Option 3: $\frac{7}{11}$
Option 4: $\frac{7}{4}$
Question : If $x^{4}+2x^{3}+ax^{2}+bx+9$ is a perfect square, where a and b are positive real numbers, then the value of $a$ and $b$ are:
Option 1: $a=5, b=6$
Option 2: $a=6, b=7$
Option 3: $a=7, b=7$
Option 4: $a=7, b=8$
Question : Directions: If A denotes +, B denotes –, C denotes × and D denotes ÷, then which of the following equations is true?
Option 1: 8 B 6 D 2 A 4 C 3 = 15
Option 2: 8 A 8 B 8 C 8 = – 48
Option 3: 9 C 9 B 9 D 9 A 9 = 17
Option 4: 3 A 3 B 3 C 3 A 3 D 3 = 4
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