Compute Each Expression

Compute Each Expression

Postby nycmath » Sat Aug 22, 2026 6:25 pm

Precalculus
David Cohen
Edition 3
Chapter 3, Set 3.4

Compute each expression, given that the functions g and k are defined as shown in the attachment.
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Re: Compute Each Expression

Postby Math Tutor » Sun Aug 23, 2026 4:35 am

With g(x) = x^2 - 3x - 6:

(a) (g + g)(x) = g(x) + g(x) = 2g(x) = 2x^2 - 6x - 12

(b) (g - g)(x) = g(x) - g(x) = 0 for every x (the zero function)

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Re: Compute Each Expression

Postby Math Tutor » Sun Aug 23, 2026 4:36 am

(c) (kg)(x) = k(x) * g(x) = 2(x^2 - 3x - 6) = 2x^2 - 6x - 12

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Re: Compute Each Expression

Postby nycmath » Sun Aug 23, 2026 8:02 am

Math Tutor wrote:With g(x) = x^2 - 3x - 6:

(a) (g + g)(x) = g(x) + g(x) = 2g(x) = 2x^2 - 6x - 12

(b) (g - g)(x) = g(x) - g(x) = 0 for every x (the zero function)


Thank you very much.

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Re: Compute Each Expression

Postby nycmath » Sun Aug 23, 2026 8:02 am

Math Tutor wrote:(c) (kg)(x) = k(x) * g(x) = 2(x^2 - 3x - 6) = 2x^2 - 6x - 12


Short and simple.

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Re: Compute Each Expression

Postby Eigenvalue » Sun Aug 23, 2026 10:46 am

10a. (g+g)(x)=x²-3x-6+x²-3x-6
=2x²-6x-12

10b. (g-g)(x)=x²-3x-6-(x²-3x-6)=0

10c.(kg)(x)= 2(x²-3x-6)
=2x²-6x-12

10d. (g+g)(-3)-(kg)(-3)
=2(-3)²-6(-3)-12-2(-3)²+6(-3)+12=0
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Re: Compute Each Expression

Postby nycmath » Sun Aug 23, 2026 12:29 pm

Eigenvalue wrote:10a. (g+g)(x)=x²-3x-6+x²-3x-6
=2x²-6x-12

10b. (g-g)(x)=x²-3x-6-(x²-3x-6)=0

10c.(kg)(x)= 2(x²-3x-6)
=2x²-6x-12

10d. (g+g)(-3)-(kg)(-3)
=2(-3)²-6(-3)-12-2(-3)²+6(-3)+12=0


Correct. The questions here are from the Cohen book.

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