Question

Define a function f : R → R by the formula
f(x) = 8x − 7.


Prove that f is onto.
Let y = R.
see screenshot below :)

Answer 1

plug the bottom stuff into the top function ....

Answer 2

what do you mean by bottom stuff?

Answer 3

f(x) = 8x - 7 ; let y=f(x)

y = 8x-7, when x = (y+7)/8

when x = (y+7)/8, what does f(x) equal?

Answer 4

replace x, in f(x), by (y+7)/8

Answer 5

y?

Answer 6

yes

Answer 7

but in the screenshot its 8( )-7=?

Answer 8

if f(x) = 8x-7, and x = (y+7)/8

f((y+7)/8) = 8((y+7)/8) - 7
= (y+7) - 7
= y

Answer 9

plug in "the value of x" into the box .....

Answer 10

ok got it
I understand now!! im just making it harder than it is :))
thank u

Answer 11

good luck :)