2007-07-04 03:37:33 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
We need (3m + 7n)(3m - 7n) = 9m^2 - kn^2. (3m + 7n)(3m - 7n) = 9m^2 - 49n^2, so k = 49.
2007-07-04 03:41:39 · answer #1 · answered by DavidK93 7 · 0⤊ 0⤋
(a+b)(a-b) = a^2 -b^2
therefore
(3m +7n )( 3m-7n) = 9 m^2 - 49 n^2
comparing with 9m^2- kn^2
k = 49
2007-07-04 10:58:31 · answer #2 · answered by qwert 5 · 0⤊ 0⤋
(3m+7n)(3m-7n)
=9m^2-49n^2
comparing the two expressions 9m^2-kn^2 and 9m^2-49n^2,we may say that k must have a value of 49
2007-07-04 10:41:42 · answer #3 · answered by alpha 7 · 0⤊ 0⤋
(3m-7n)(3m+7n) = 9m^2 - 49n^2
k = 49
2007-07-04 10:43:56 · answer #4 · answered by UnknownD 6 · 0⤊ 0⤋
(3m+7n)(3m-7n)
=(3m)^2-(7n)^2
=9m^2-49n^2
Therefore, k=49
2007-07-04 10:44:38 · answer #5 · answered by Jain 4 · 0⤊ 0⤋