MCQ
If $\text{x}+\frac{1}{\text{x}}=2,$ then $\text{x}^3+\frac{1}{\text{x}^3}=$
- A8
- B14
- C64
- D2
✓
Answer
- 2
Solution:
On cubing we get
$\Big(\text{x}+\frac{1}{\text{x}}\Big)^3=\text{x}^3+\Big(\frac{1}{\text{x}^3}\Big)+3\text{x}\times\frac{1}{\text{x}}\Big(\text{x}+\frac{1}{\text{x}}\Big)$
$\Rightarrow2^3=\text{x}^3+\Big(\frac{1}{\text{x}^3}\Big)+3\times2$
$\Rightarrow\text{3}^3+\Big(\frac{1}{\text{x}^3}\Big)=8-6$
$\Rightarrow\text{x}^3+\Big(\frac{1}{\text{x}^3}\Big)=2$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
If the diagonals of a rhombus of a rhombus are 18cm and 24cm respectively, then its side is equal to:
- 16cm.
- 15cm.
- 20cm.
- 17cm.
Observe the table given below and choose the correct alternative: The class mark for R is:
| Column | P | Q | R | S | T | E |
| Marks scored | 30-40 | 40-50 | 50-60 | 6-70 | 70-80 | 80-90 |
| Number if students | 4 | 8 | 12 | 10 | 7 | 4 |
A coin is tosses 1000 times, if the probability of getting a tail is $\frac{3}{8},$ how many times head is obtained?
→- 525
- 375
- 625
- 725
The value of xp-q xq-r xr-p is equal to:
A solid cylinder is melted and cast into a cone of same radius. The heights of the cone and cylinder are in the ratio
Which of the following polynomials has (-3) as a zero?
If a + b + c = 0 then (a3 + b3 + c3) is:
- 0
- abc
- 2abc
- 3abc
The equation x = 7 in two variables can be written as:
The factors of $8 a^3+b^3-6 a b+1$, are
→