Question

If 5x+1/5x=7;find the value of 125x3+1/125x3

Answer 1

x=

Step-by-step explanation:

$5x + 1 = 7 \times 5x = 5x + 1 = 35 x = x = - 1 \div 30$

Answer 2

Answer:

The correct answer is 322

Step-by-step explanation:

Given problem

If 5x+ (1/5x) = 7,  find the value of 125 x³+ 1/125 x³

we know that  (a+b)³ = a³ + b³ + 3ab (a+b)  

here a = 5x and b = 1/5x  

⇒ 5x+ (1/5x) = 7,  apply cube on both sides

⇒ [5x+ (1/5x) ]³ = 7³

⇒ $(5x)^{3} + (\frac{1}{5x})^{3} + 3 (5x)(\frac{1}{5x})( 5x + \frac{1}{5x} ) = 343$  

⇒ simplify the above equation

      = 125x³ + $\frac{1}{125x^{3} }$ + 3(1) (7)  = 343              [ 5x +  1/5x = 7]

     = 125 x³ + $\frac{1}{125} x^{3}$ = 343 - 21 = 322