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What's the value of X

Whats The Value Of X class=

Sagot :

Lilith
[tex](x+1)^2 -(x-1)^2 = 32 \\ \\x^2+2x+1 -(x^2-2x+1)=32\\ \\x^2+2x+1-x^2+2x-1=32\\ \\ 4x =32\ \ / :4 \\ \\x=\frac{32}{4}\\ \\x=8 [/tex]
AL2006
All the busy-work is on the left side.

1). Take care of the (x+1)² . . .

(x + 1)² = x² + 2x + 1

2).  Take care of the (x-1)² . . .

(x - 1)² = x² - 2x + 1

The problem says that (the first expression) minus (the second expression) is 32 .

(x² + 2x + 1) - (x² - 2x + 1) = 32

Can you handle this ?
Only one more touchy point to take care of . . . removing the second parentheses.
Since there's a negative sign before it, that changes the sign of everything inside:

(x² + 2x + 1) PLUS (- x² + 2x - 1) = 32

Now you can just erase all the parentheses:

x² + 2x + 1   -  x² + 2x - 1 = 32

Now I'm just going to write the things on the left side in a different order,
without changing anything:

x² - x²     + 2x + 2x        + 1 - 1 = 32

Isn't that neat ? ! ?
What you have now is:

4x = 32

Divide each side by 4 :

x = 8


Just watch how slick that works:

(x + 1)² - (x - 1)² = ?

(x + 1) = 9      (x - 1) = 7

(9)² - (7)² = 81 - 49 = . . . . . . . . 32 !

спасибо
Удачи