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You are using an out of date browser. It may not display this or other websites correctly.You should upgrade or use an alternative browser. Solving (f+g)(x)=0 using f(x) and g(x)

• Thread starter Howdoyoumath
• Start date Jul 7, 2019

H

Howdoyoumath

New member

Joined Jul 5, 2019 Messages 3 I have another question that I don't understand. f(x)=x^2−6x and g(x)=x+6, find (f+g)(x)=0 (f-g)(x)=12 (fg)(x)=-36 (f/g)(x)=-1 It says my answers are incorrect and i plugged in f(6)=(6)^2-6(6) and for g(-6)=(-6)+6 f(6)=0 g(-6)=0 Where did I go wrong? Also should they always =0? Also, should f and g have the same f(6) or g(6) value?

Steven G

Elite Member

Joined Dec 30, 2014 Messages 14,603 Let's see where you went wrong. (f+g)(6) = f(6) + g(6) = 0 + 12 = 12, NOT 0 (f+g)(-6) = f(-6) + g(-6) = 72 + 0 = 72, NOT 0 Just because f(6) = 0 does NOT imply that (f+g)(6) = 0 You first have to find (f+g)(x) and figure out when that equals 0

Otis

Elite Member

Joined Apr 22, 2015 Messages 4,589

Howdoyoumath said: … i plugged in f(6) … and for g(-6) … Click to expand...

Howdy, Howdo… You solved f(x)=0 and g(x)=0 thinking that (f+g)(x) would then be 0+0. It doesn't work that way; for one reason, the variable x cannot represent two different values (6 and -6) at the same time. Here's how to proceed: (f+g)(x) = 0 We know the left-hand side is f(x)+g(x), so we add the given expressions for f(x) and g(x) together. That will give us the expression for (f+g)(x). x^2 − 6x + x + 6 = 0 That is the equation you need to solve, to find all values of x for which the equation (f+g)(x)=0 is true. ? You must log in or register to reply here. Share: Facebook X (Twitter) Reddit Pinterest Tumblr WhatsApp Email Share Link

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