Solve the equations: x+3^y=3 and (x-1)^2-9^y=10 for x and y

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justaguide | College Teacher | (Level 2) Distinguished Educator

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The equations `x + 3^y = 3` and `(x-1)^2 - 9^y = 10` have to be solved for x and y. If `3^y = z` , the system is changed to:

`x + z = 3` ...(1)

`(x - 1)^2 - z^2 = 10` ...(2)

Substitute z = 3 - x from (1) into (2)

=> `(x - 1)^2 - (3 - x)^2 = 10`

=> `x^2 - 2x + 1 - 9 - x^2 + 6x = 10`

=> 4x - 8 = 10

=> `x = 9/2`

z = -1.5

As `z = 3^y` it cannot be negative.

The system of equations does not have a real solution.

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vaaruni | High School Teacher | (Level 1) Salutatorian

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Given,   x + 3y = 3   ------(1)   and

             (x-1)2 – 9y = 10   -------(2)

Taking equation (1)    x + 3y = 3

Let   3y = z     then,  equation (1) à x + 3y= 3    

          =>  x + z = 3

          =>  z = 3 – x  -----(3)

Taking  equation (2)   ->

 (x-1)2 – 9y = 10

=> (x-1)2 – (3)2y = 10

=> (x-1) 2 - ( (3)y)2 = 10

=> (x-1) 2 - z2 = 10  [ since, 3y = z ]

=> (x) 2 – 2x +1- (3 – x)2 = 10  [ substituting  value of ‘z’ from equation (3) ]

=> x2 -2x +1- 9+ 6x- x2 = 10

=>  4x- 8 = 10

=> 4x = 18

=> x = 18/4 = 4.5

x = 4.5

substituting value of x in equation (1) x + 3y = 3

We get --> 4.5 + 3y = 3       

=>  3y    = 3 - 4.5

=> 3y  = (-1.5) 

Value of  ‘y’  will be imaginary  

 x = 4.5   and  value  of  ‘y’  will be---->Answer

    

  x = 4.5  ---->Answer

vaaruni's profile pic

vaaruni | High School Teacher | (Level 1) Salutatorian

Posted on

 

Given,   x + 3y = 3   ------(1)   and

             (x-1)2 – 9y = 10   -------(2)

Taking equation (1)  -->   x + 3y = 3

Let   3y = z     then,  equation (1) à x + 3y= 3    

          =>  x + z = 3

          =>  z = 3 – x  -----(3)

Taking  equation (2)   ->

 (x-1)2 – 9y = 10

=> (x-1)2 – (3)2y = 10

=> (x-1) 2 - ( (3)y)2 = 10

=> (x-1) 2 - z2 = 10  [ since, 3y = z ]

=> (x) 2 – 2x +1- (3 – x)2 = 10  [ substituting  value of ‘z’ from equation (3) ]

=> x2 -2x +1- 9+ 6x- x2 = 10

=>  4x- 8 = 10

=> 4x = 18

=> x = 18/4 = 4.5

 x = 4.5  ---->Answer

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