Can anyone help me with this question please;
factorise a²-9b²
Thankyou
2007-05-24 09:07:05 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
a²-9b²
= a²-(3b)²
= (a-3b)(a+3b)
because a²-b² = (a-b)(a+b).
2007-05-24 12:11:40 · answer #1 · answered by Kemmy 6 · 0⤊ 0⤋
This is known as 'The difference of two squares' and is very important as it comes up time after time.
In general x²-y² = (x+y)(x-y) (it expands to x²+xy-xy-y²)
In this case a²-9b² can be rewritten as a²-(3b)² so can be factored into (a+3b)(a-3b)
2007-05-24 11:02:28 · answer #2 · answered by welcome news 6 · 0⤊ 0⤋
How to factor a^2 - 9b^2.....
Rewrite as a^2 -(3b)^2
Knowing that a^2 - b^2 = (a + b)(a - b)
a^2 -(3b)^2 = (a + 3b)(a - 3b)
If you feel like it, you can check your work by multiplying....
2007-05-24 09:12:21 · answer #3 · answered by John G™ 3 · 0⤊ 0⤋
I assumed you meant Factoring. Anyway, I think it's
(a-3b) (a+3b)
2007-05-24 09:13:23 · answer #4 · answered by Lady W. 1 · 0⤊ 0⤋
a^2 - 9b^2
=(a)^2 - (3b)^2
=(a+3b)(a-3b)........use formula^2-b^2=(a+b)(a-b)
2007-05-27 20:57:51 · answer #5 · answered by billako 6 · 0⤊ 0⤋
a^2-9b^2
(a+3b)(a-3b)
2007-05-25 02:41:05 · answer #6 · answered by srirad 2 · 0⤊ 0⤋
a²-9b²
(a + 3b)(a - 3b)
.
2007-05-24 09:10:29 · answer #7 · answered by Robert L 7 · 1⤊ 0⤋
=( x - 3b )(x+3b)
2007-05-24 09:17:55 · answer #8 · answered by muhamed a 4 · 0⤊ 0⤋