Find the coefficient - calculus questions

[vorcil]

1:
If g(x) = 2x^2 – 5x then g(2+h) =

my working

2(2+h)^2 -5(2+h)
( 2((2+h)*(2+h)) ) - 5(2+h)
2(4 + h^2 + 4h) - 10 -5h
8 + 2h^2 + 8h - 10 -5h

-2 + 3h + 2h^2

2:
Find the coefficient of x in (2x – 7)^2.
isn't it 2?

 

[queenofbabes]

#1 looks correct.
#2 you'll have to expand it first!

 

[vorcil]

#1 looks correct.
#2 you'll have to expand it first!

Find the coefficient of x in (2x – 7)2.

2x-7 * 2x-7
4x^2 - 14x - 14x + 49

4x^2 - 28x + 49

coefficient is 4-28?
so -24?
or 4, or 28

i'm pretty sure it's 4, because it's infront of the x^2, but the 28 infront of x could also be a coefficient?

 

[rock.freak667]

Coefficient fof x is the number in front of x...so in 4x^2 + (- 28)x + 49 what is that?

 

[vorcil]

Coefficient fof x is the number in front of x...so in 4x^2 + (- 28)x + 49 what is that?

there is a 4 in front of the x^2,
and -28 infront of the x.

if you meant the number infront of just the x, then it's -28
if you meant the number infront of the x, in x^2 then it's 4

which one do i choose? the power functioned x or the x without it?

i'm assuming it's the x without it because if there were more functions, like a cubic polynomial, with like ax^4 + bx^3 + cx^2 + dx + e, then it'd get confusing

so -28 is my awnser?

 

[rock.freak667]

so -28 is my awnser?

Yes.


But if you had

ax³+bx²+cx+d

The coefficient of x³ is a
The coefficient of x² is b
The coefficient of x is c

and so forth.