Question

How do i find the excluded value of this denominator?
r^3−r^2−49r+49

Answer 1

Let the denominator = 0

Answer 2

how?

Answer 3

Solve the eqn = 0

Answer 4

i learned that we factor it first and equal it to zero

Answer 5

how do i solve it? it doesn't have a common factor

Answer 6

try finding a factor using factor theorem

Answer 7

thanks i'll learn that go learn that
i haven't learned that yet

Answer 8

x-7 is worth trying (as last term = 7^)

f(7) = 343 - 49 - 343 + 49 = 0

ok so (x-7) is a factor

now find any other factors by dividing by x-7

Answer 9

factor theorem if f(x) is divisible by x-a then f(a) = 0

Answer 10

r^2 +6r - 7
----------------
r-7 ) r^3−r^2 −49r+49
r^3 -7r^2
--------
6r^2 - 49r
6r^2 - 42r
---------
-7r + 49

Answer 11

r^2 +6r - 7 = (r+7)(r-1)

so factors of f(r) =

(r-7)(r+7)(r-1)

Answer 12

so excluded value is value of f(r) when r=7,-7 or 1

Answer 13

Yes