Question

If f:R-R is defined as f(x)=2x2-1,find the pre images of 17,4​

Answer 1

Answer:

i) x=3 and x=(-3)

ii) x= √(5/2) and x= -√(5/2)

Step-by-step explanation:

f(x)=2x²-1

To find the pre-image of a number, just substitute the given number in f(x).

Pre-image of 17,

17= 2x²-1

2x²=18

x²=9

x=3 or x=(-3) (because domain is R, -ve numbers are valid)

Pre-image of 4,

4=2x²-1

2x²= 5

x²= 5/2

x= √(5/2) or x= -√(5/2)