I got a Function Math question.?

Question

Let the function f be defined by f(x)=2x - 1. If 1/2f(squareroot of t)= 4, what is the value of t ?


Ok for that second equation its written as, one half times f of the square root of t equals four.

My school book says the answer is 81/ 4 (81 over 4).

Answer 1

(1/2) * f(sqrt(t)) = (1/2) * (2sqrt(t)-1) = 4
sqrt(t) - 1/2 = 4
sqrt(t) = 9/2
(sqrt(t))^2 = (9/2)^2
t = 81/4

Answer 2

Let's see...f(x) = 2x-1

Let x=sqrt(t)

The equation you have to solve,

0.5f(sqrt(t))=4

so,

0.5(2*sqrt(t)-1)=4

Multiply by 2 both sides of the equation,

2*sqrt(t) - 1 = 8

or
2*sqrt(t) = 9

dividing by 2 both sides,

sqrt(t) = 9/2

Squaring both sides of the equation

t = 81/4,

which is the answer the book provided.

Answer 3

answer is 81/4