If a-b=1, then the value of a³-b³-3 a b will be · ABC26GN1207

Subject: General Aptitude · Chapter: Simplification

If $a-b=1$, then the value of $a^{3}-b^{3}-3 a b$ will be

(a)- 3

(b)- 1

(c)1

(d)3

Answer

Answer (as printed): C

Explanation

$$\begin{aligned} a-b=1 & \Rightarrow(a-b)^{3}=1^{3}=1 \Rightarrow a^{3}-b^{3}-3 a b(a-b)=1 \\ & \Rightarrow a^{3}-b^{3}-3 a b=1[\because a-b=1] \end{aligned}$$

Explanation as extracted from the printed page; notation may be imperfect.

Study loop for Simplification

1. Practise the PYQsPrevious-year questions, with answers

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