Remember that a function is a rule that assigns to each element in the domain one and only one element in the range. If f(x) = 8x+4, find the domain value, a, such that f(a)=1.6

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hala718's profile pic

hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted on

f(x) = 8x +4

Given that f(a) = 1.6

We need to find the values of a.

We will substitute with x= a into the function f(x).

==> f(a) = 8a +4 = 1.6

Now we will solve for a.

==> 8a = 1.6 -4 = -2.4

Now we will divide by a.

==> a = -2.4/8 = -0.3

Then there are only one values of a that satisfies the function which is a= -0.3

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

In other words, we'll have to determine what is the x value that whose correspondent y value, through the given expression of the function, is 1.6.

We know that f(x) = y, where the rule that assigns to x a y value is f(x) = 8x+4.

8x + 4 = 1.6

We'll subtract 4 both sides, in order to isolate x to the left side:

8x = 1.6 - 4

8x = -2.4

Now, we'll divide by 8 both sides:

x = -2.4/8

x = -0.3 or x = -3/10

Since the value of x that makes y to be 1.6 is denoted as a, then a = -0.3.

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