Question

Someone help mewith this quadratic equation pls:

Your classmate solved as follows:
(x+5)(x-1)=2

x+5=2 x-1=2
x=2-5 x=1+2
x=-3 x=3

Your teacher said this was wrong because the values didnt check. Explain what is wrong with your classmate's solution.

Answer 1

more information needed

Answer 2

It needs a lot more info.

Answer 3

^mmhmm how did he solve it

Answer 4

ya it really does

Answer 5

lol sorry there ya go i hit post button too early

Answer 6

the problem is , that step is not valid. only if (x-a)(x-b) = 0, can you say that
(x-a) =0 or (x-b) = 0.
it is false that
(x-a) (x-b) = c , that (x-a) = c , (x-b) = c

Answer 7

it is false generally * ( it may be true in some fluke example)

Answer 8

Or to say it another way,
it is false (generally) that the equation
(x-a)(x-b)= c
implies
(x-a) = c or x-b = c

It is only true in the case when c = 0

Answer 9

so you cannot go from the step ( x+5 )( x -1 ) = 2 to the next step (x+5) =2 , x-1=2.
this is not valid . thats why when we solve quadratic equations we set them equal to zero, and then factor

Answer 10

the zero product property lets you go from (x+5)(x-2) = 0 to the step (x+5) = 0 or (x-2)=0

Answer 11

Thank you so much