Simplification
- If x + 1/x = 6, then x4 + 1/x4 is ?
-
View Hint View Answer Discuss in Forum
x + 1/x = 6
On squaring both sides, we get
(x + 1/x)2 = (6)2
⇒ x2 + 1/x2 + 2 = 36
⇒ x2 + 1/x2 = 34
Correct Option: B
x + 1/x = 6
On squaring both sides, we get
(x + 1/x)2 = (6)2
⇒ x2 + 1/x2 + 2 = 36
⇒ x2 + 1/x2 = 34
On squaring both sides, we get
(x2 + 1/x2)2 = (34)2
⇒ x4 + 1/x4 + 2 = 1156
⇒ x4 + 1/x4 = 1154
- If x + 1/x = 2, then what is value of x - 1/x ?
-
View Hint View Answer Discuss in Forum
Given that, x + 1/x = 2 ...........................(i)
On squaring both sides, we get
(x + 1/x)2 = 4
⇒ x2 + 1/x2 + 2 = 4
⇒ x2 + 1/x2 = 2 ...............................(ii)
Now, we have
(x - 1/x)2 = (x2 + 1/x2) - 2x X 1/xCorrect Option: A
Given that, x + 1/x = 2 ...................(i)
On squaring both sides, we get
(x + 1/x)2 = 4
⇒ x2 + 1/x2 + 2 = 4
⇒ x2 + 1/x2 = 2 ..................................(ii)
Now, we have
(x - 1/x)2 = (x2 + 1/x2) - 2x X 1/x
now put the value of x2 + 1/x2
(x - 1/x)2 = 2 - 2 = 0 [from Eq. (ii)]
∴ x - 1/x = 0
- If x + 1/x = 3, then x5 + 1/x5 is equal to ?
-
View Hint View Answer Discuss in Forum
x + 1/x = 3 ................. (i)
On squaring both side, we will get
(x + 1/x)2 = (3)2
Correct Option: A
x + 1/x = 3 ........................ (i)
On squaring both side, we will get
(x + 1/x)2 = (3)2
Use the Square algebra formula (a + b)2 = a2 + 2ab + b2
⇒ x2 + 1/x2 + 2 = 9
⇒ x2 + 1/x2 = 7 ..................(ii)
Again squaring both sides, we will get
(x2 + 1/x2)2 = (7)2
Use the Square algebra formula (a + b)2 = a2 + 2ab + b2
⇒ x4 + 1/4 + 2 = 49
⇒ x4 + 1/x4 = 47 .....................(iii)
On cubing the equation (i) both side, we will get
(x + 1/x)3 = (3)3
Use the cube algebra formula (a + b)3 = a3 + 3a2b + 3ab2 + b3
⇒ x3+ 1/x3 + 3(x + 1/x) = 27
⇒ x3 + 1/x3 + 9 = 27 [∴ (x + 1/x) = 3]
⇒ x3 + 1/x3 = 18 ...................(iv)
On multiplying Eqs. (i) and (iii) , we get
∴ (x4 + 1/x4) (x + 1/x) = 47 x 3
⇒ x5 + 1/x5 + x3 + 1/x3 = 141
⇒ x5 + 1/x5 + 18 = 141 [from Eq. (iv)]
⇒ x5 + 1/x5 = 123
- 3x + 2y = 12 and xy = 6, them the value of 9x2 + 4y2 is ?
-
View Hint View Answer Discuss in Forum
Given equation are
3x + 2x = 12 ...................(i)
xy = 6 ..............................(ii)
On squaring Eq. (i) on both sides and put the value of xy and solve the equation.Correct Option: C
Given equation are
3x + 2y = 12 ..............(i)
xy = 6 .........................(ii)
On squaring Eq. (i) on both sides, we will get
(3x + 2y)2 = (12)2
⇒ 9x2 + 4y2 + 12xy = 144
put the value of xy
⇒ 9x2+ 4x2 = 144 - 72 = 72
⇒ 9x2+ 4x2 = 72
- (4 x 4 x 4 x 4 x 4 x 4)5 x (4 x 4 x 4 )8 ÷ (4)3 = (64)?
-
View Hint View Answer Discuss in Forum
(4 x 4 x 4 x 4 x 4 x 4)5 x (4 x 4 x 4)8 ÷ (4)3 = (64)?`
Apply the law of Fractional Exponents and Laws of Exponents
if a multiply n times a x a x a x....up to n times, then
a x a x a x a ......up to n times = an
⇒ (46)5 x (43)8 x 1/(4)3 = (43)?Correct Option: A
(4 x 4 x 4 x 4 x 4 x 4)5 x (4 x 4 x 4)8 ÷ (4)3 = (64)?
Apply the law of Fractional Exponents and Laws of Exponents
if a multiply n times a x a x a x....up to n times, then
a x a x a x a ......up to n times = an
By simplifying the equation
⇒ (46)5 x (43)8 x 1/(4)3 = (43)?
⇒ (4)30 x (4)24/(4)3 = (4)3 x ?
⇒ 430 + 24 - 3 = 43 x 7
And comparing the exponents both the sides
⇒ 451 = 43 x ? ⇒ 3 x ? = 51
∴ ? = 51/3 = 17