Question

If f(x) = 2x2 − 10, find f(5).
i got to 15=2x2 but i cant figure out what to do after

Answer 1

f(x) = 2x^2 − 10

f(5) = 2(5)^2 − 10

Did you get this far?

Answer 2

yes then i added 10 to each side

Answer 3

why? you only need to do that if you're solving for x

Answer 4

simply evaluate 2(5)^2 − 10

Answer 5

oh oops

Answer 6

that's ok

Answer 7

i know, she wanted to add 10 to both sides, but you only do that when solving for x

Answer 8

how am i going to find x?

Answer 9

f(5) means find f(x) when x = 5

Answer 10

you already know what x is in this case

Answer 11

so its 5

Answer 12

f(x) = 2x^2 - 10

so replace EVERY x with 5 to get

f(5) = 2(5)^2 - 10

Answer 13

then 2 times 5?

Answer 14

So your job now is to find 2(5)^2 - 10

Hint:

(5)^2 means 5*5

and 2(5)^2 is 2 times 5 squared

Answer 15

close, but no

Answer 16

PEMDAS says you have do exponents before multiplication

Answer 17

25 then 10?

Answer 18

f(5) = 2(5)^2 - 10

f(5) = 2(25) - 10


Note: 5^2 = 5*5 = 25

Answer 19

now multiply 2 and 25 because 2(25) means 2 times 25

Answer 20

so 50

Answer 21

then subtract 10

Answer 22

40

Answer 23

perfect

Answer 24

So here's the complete step by step solution


f(x) = 2x^2 - 10


f(5) = 2(5)^2 - 10


f(5) = 2(25) - 10


f(5) = 50 - 10


f(5) = 40

Answer 25

thank you

Answer 26

you're welcome