solve f(x)=2x^2+4x-6 when x= -1.?

Question

I don't understand the expanation in my book. Where do they get --16 in place of the one when factord out.

Answer 1

Books are not always right.

Answer is none other than -8

f(-1)=2(-1)^2+4(-1)-6
f(-1)=2(1)-4-6
f(-1)=2-4-6
f(-1)=-8

thats the final answer and im 300% sure

Answer 2

Substitute x = -1 into the formula.
f(x)=2x^2+4x-6
=2(-1)^2+4(-1)-6
=2-4 -6
=-8
f(x) =-8

If I am not mistaken, -1 is not a factor.

2x^2+4x-6
x^2+2x-3
(x+3)(x-1)
x = 1 is a factor.
or
x = -3


I don't think that the value x = -1, but I may be wrong. Also, I don't know how to maker --16
+16.

Dexter T

Answer 3

The question should say 'Evaluate f(x) = .... when x = -1', or 'Solve f(x) = 0 where f(x) = 2x^2 + 4x + 6'. Then it would make sense. Is this an Edexcel question?

Answer 4

I don't know about -16. From your equation, I'd say:
2x^2 = 2
4x = -4
-6 = -6
add them together:
2 - 4 - 6 = -8,
unless there's something we're both missing!

Answer 5

If x=-1
Then Then put -1 wherever there is x,
f(-1)=2(-1)^2+4(-1)-6
=2(1)-4-6 [as(-1)^2 = 1]
=2-10=-8

Answer 6

are you sure that is what the book says? -16?

its not a factoring problem, you just sub -1 for x and solve like normal

f(x) is just a fancy way of saying y

so read y = 2(-1)^2...

Answer 7

section a million: L=(36x^4-64x^2)/(6c^2+8x) section 2: it fairly is a great distinction of squares. There are surely 2 words and that they are the two squares and the sign indoors the middle is unfavorable. section 3: That divides rather fairly. it would be L=6x^2-8x. section 4 is a similar ingredient, curiously like.

Answer 8

f(x) = 2x^2 + 4x - 6
f(1) = 2(1)^2 + 4(1) - 6
f(1) = 4 + 4 - 6
f(1) = 2 (final answer)

*I don't understand your explaination either.

Answer 9

f(x) =2x(x+3)-2(x+3)
f(x) = (x+3)(2x-2)
f(x) = 2(x+3)(x-1)
when x= -1, f(-1) =2(-1+3)(-1-1)
Hence f(-1) = (2)*(2)*(-2) = -8

Answer 10

Sowwy - You're on your own