Math Is Fun Forum

nycguitarguy

Member

Registered: 2024-02-24

Posts: 542

Find the Value of B

If f(x) = 3x^2 - Bx + 4 and f(-1) = 12, what is the value of B?

Let me see.

Let f(x) = 12

12 = 3(-1)^2 - (-1)B + 4

12 = 3 + B + 4

12 = B + 7

12 - 7 = B

5 = B

Do you agree?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,196

Re: Find the Value of B

Yes.

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

KerimF

Member

From: Aleppo-Syria

Registered: 2018-08-10

Posts: 165

Re: Find the Value of B

Let me see it in reverse.

f(x) = 3x^2 - Bx + 4  with x=-1 and B=5
f(-1) = 3*((-1)^2) - (5)*(-1) + 4
f(-1) = 3 + 5 + 4 = 12

Your B=5 is right for sure.

nycguitarguy

Member

Registered: 2024-02-24

Posts: 542

Re: Find the Value of B

Yes.

Perfect. I found this question to be a bit interesting.

nycguitarguy

Member

Registered: 2024-02-24

Posts: 542

Re: Find the Value of B

Let me see it in reverse.

f(x) = 3x^2 - Bx + 4  with x=-1 and B=5
f(-1) = 3*((-1)^2) - (5)*(-1) + 4
f(-1) = 3 + 5 + 4 = 12

Your B=5 is right for sure.

This is not your typical classroom question but interesting nonetheless. This is what I like about textbooks. There are tons of questions normally not taught in the classroom.