Question

somebody gave me an answer earlier but i dont get it im sorry
Your classmate solved
(x+5)(x-1)=2 as follows:

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

Your teacher said this was wrong because the values did not check. Explain what is wrong with your classmate’s solution.

Answer 1

Thats wrong

Answer 2

whats wrong?

Answer 3

x+5=2 x-1=2
if these were to get you 2 then in the answer u'd end up with 4

Answer 4

and your answer has to be 2
not 4

Answer 5

For one...
\((-3 + 5)(-3 - 1) \ne 2\)

Answer 6

\((3 + 5)(3 - 1) \ne 2\) either

Answer 7

(x+5)(x-1)=2
so use FOIL to solve
(x+5)(x-1)=2
x^2 + 5x - 1x - 5 = 2
x^2 + 4x - 7 = 0
now use the quadratic equation to solve for x
you should arrive at x = 1.3 ish and -5.3 ish

Answer 8

In order to solve such problems we ned to multiply both the brackets first and then bring 2 to left side.
(x+5)(x-1)=2

x(x-1) +5(x-1) -2=0
\[\huge x^2 -x + 5x- 5 -2 =0\]
\[\huge x^2 + 4x- 7=0\]
now factorize it and you will find the correct answer,

Answer 9

thank you guys so much :)

Answer 10

Whenever you have an equation of the form
(x - m)(x - n) = p

You essentially have a quadratic equation since the product of two binomials will always form a quadratic expression. Furthermore after expanding the product of two binomials, you must put it in form \(ax^2 + bx + c = 0\) before attempting to solve it. In other words, the left side must be a quadratic expression and the right side must be equal to zero BEFORE attempting to solve for x. If you proceed in any other manner, you will get the wrong answer.

Answer 11

okay thank you :)

Answer 12

Also you should know that if what you had was of the form \((x - m)(x - n) = 0\), then you would be able to use the zero product property to split the equation in to two equations such as

x - m = 0
x - n = 0

Answer 13

Again, you can only do this when the product of two binomials equal zero.

Answer 14

yes i know that thanks :)

Answer 15

If that's the case, and you know what to do now, how would you go about solving

(x - 3)(x + 4) = 5 ?

Answer 16

its just like the problem below

Answer 17

I'd like to see you attempt to solve the problem of course just to make sure you know what you are doing.

Answer 18

im going to finish this one first okay (the problem below) im not yet done with it :(

Answer 19

What problem are you referring to?

Answer 20

the one i posted

Answer 21

Post it here.

Answer 22

okaaay

Answer 23

\[\frac{ x=-4+\sqrt{4^{2}}-(4)(1)(-7) }{ 2 (1) }\]

Answer 24

and \[\frac{ x=-4 - \sqrt{4^{2}}-(4)(1)(-7) }{ 2(1) }\]

Answer 25

eq1: \[\frac{ x=-4+\sqrt{44} }{ 2(1) }\]

Answer 26

eq2: \[\frac{ x=-4-\sqrt{44} }{ 2(1) }\]

Answer 27

eq1: 1.32 & eq2: -5.32 (rounded off)

Answer 28

am i correct or not :c

Answer 29

Well, I think you meant to put it in this form:

\[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]

Perhaps you should review a few lessons o how to post fractions and equations using \(\LaTeX\)

Answer 30

ohmygod what is dat omg im only a 9th grader :(((((

Answer 31

but is my answer correct?