Question

what are the zeros of the related function to this equation x^2-4x-21=0

Answer 1

To factor this you need 2 numbers, whose product is -21 ans whose sum is -4

Answer 2

it factors to
(x + a)(x + b) = 0
where a and b are the 2 numbers

Answer 3

so the zeros are -21 and 4 or just 2?

Answer 4

no a and b have to be found first
ab = -21
a + b = -4

can you solve this system of equations?

Answer 5

a and b are the 2 numbers welshfella talked about

Answer 6

a+b+-4
-7+3?

Answer 7

right -7*3 = -21
and -7 + 3 = -4

Answer 8

so we have
(x - 7)(x + 3) = 0

now it easy to find the zeroes

Answer 9

can you solve that?

Answer 10

you have 2 expressions multiplied together to give zero
therefore either one of them must equal zero
so we have

x - 7 = 0 and x + 3 = 0

solve these 2 equations and you have your answer

Answer 11

x=7 & x=3?

Answer 12

not quite

Answer 13

one of them should be negative

Answer 14

-7?

Answer 15

x + 3 = 0
add -3 to both sides

Answer 16

-3... my bad

Answer 17

x + 3 - 3 = -3
x = ?

Answer 18

yes answer is {-3,7}

Answer 19

- this is called the solution set

Answer 20

im really lost im sorry

Answer 21

which part are you lost on?

Answer 22

the question is what are the ZEROS of the related function im just confused at finding the zeros I guess...

Answer 23

the zeros are the values of x which make the function equal to zero That is why you write x^2 - 4x - 21 = 0. They correspond to the points where the function cuts the x-axis ( where the function = 0)

Answer 24

the graph looks a bit like this