Question

Find x  if f(

x) = 2x  + 7 and f( x ) = -1.

Answer 1

f(x) = 2x+7

-1 = 2x+7
-7 -7

-8 = 2x

-8/2 = 2x/2

-4 = x

x = -4

Answer 2

Answer: The required value of x is -4.

Step-by-step explanation: We are given to find the value of x if :

`f(x)=2x+7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(i)\\\\f(x)=-1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(ii)`

Since both the equations (i) and (ii) are the values of x, so comparing the equations, we get

`2x+7=-1\\\\\Rightarrow 2x=-1-7\\\\\Rightarrow 2x=-8\\\\\Rightarrow x=-(8)/(2)\\\\\Rightarrow x=-4.`

Thus, the required value of x is -4.