help!!!!!
x^2-81=
x^2-64=
thanks
ps. explain too x
how do i factorise these expressions?
2009-03-27 4:34 pm
回答 (8)
2009-03-27 4:37 pm
✔ 最佳答案
a² - b² = (a - b) * (a + b)<=>
x² - 81 = (x - 9) * (x + 9)
because a² = x² so a = x
and
b² = 81 so b = 9
*******
x² - 64 = (x - 8) * (x + 8)
because
a² = x² so a = x
and
b² = 64 so b = 8
2009-03-27 5:42 pm
a^2 - b^2 = (a + b)(a - b)
1)
x^2 - 81
= x^2 - 9^2
= (x + 9)(x - 9)
2)
x^2 - 64
= x^2 - 8^2
= (x + 8)(x - 8)
1)
x^2 - 81
= x^2 - 9^2
= (x + 9)(x - 9)
2)
x^2 - 64
= x^2 - 8^2
= (x + 8)(x - 8)
2009-03-27 4:54 pm
Using the formula:
a² - b² = (a - b)(a + b)
x² - 81
= x² - 9²
= (x - 9)(x + 9)
x² - 64
= x² - 8²
= (x - 8)(x + 8)
Done
a² - b² = (a - b)(a + b)
x² - 81
= x² - 9²
= (x - 9)(x + 9)
x² - 64
= x² - 8²
= (x - 8)(x + 8)
Done
2009-03-27 4:49 pm
a^2-b^2=(a-b)(a+b)
b=9
b=8
b=9
b=8
2009-03-27 4:45 pm
You are after this.
( x - a )( x + a ) = x² - a²
x² - 81 => Guess the value of a ?
a = 9 => ( x - 9 )( x + 9 )
x² - 64 => Guess the value of a ?
a = 8 => ( x - 8 )( x + 8 )
Works for others as well, you can create your own questions...
x² - 144 => Guess the value of a ?
a = 12 => ( x - 12 )( x + 12 )
etc...
( x - a )( x + a ) = x² - a²
x² - 81 => Guess the value of a ?
a = 9 => ( x - 9 )( x + 9 )
x² - 64 => Guess the value of a ?
a = 8 => ( x - 8 )( x + 8 )
Works for others as well, you can create your own questions...
x² - 144 => Guess the value of a ?
a = 12 => ( x - 12 )( x + 12 )
etc...
2009-03-27 4:41 pm
(x-9)*(x+9)
(x-8)*(x+8)
(x-8)*(x+8)
2009-03-27 4:40 pm
x^2 is a square number, it is x squared. 81 and 64 are also square numbers, 9 and 8 squared respectively. The method used to factorize the expressions is known as 'Difference of Two Squares'.
x^2-81 = (x-9)(x+9) since the +9x and -9x will cancel out.
The same method can be used to factorize x^2-64.
x^2-81 = (x-9)(x+9) since the +9x and -9x will cancel out.
The same method can be used to factorize x^2-64.
2009-03-27 4:39 pm
x^2-81=
take the square root of both. x^2 = x 81>9
answer is (x + 9) (x - 9)
x^2-64=
do the same. You can only use this method if you are subtracting the 2 numbers.
answer is (x +8) (x-8)
take the square root of both. x^2 = x 81>9
answer is (x + 9) (x - 9)
x^2-64=
do the same. You can only use this method if you are subtracting the 2 numbers.
answer is (x +8) (x-8)
收錄日期: 2021-05-01 12:11:05
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090327083456AAaXD7Y