Question

If m²-n² = 7 , where m,n € Z, then no.of ordered pairs ( m,n ) is
A. 1
B. 2
C. 3
D. 4

Please ans it fast

Answer 1

Answer:

option (D) is correct.

Explanation:

We have ,

m²-n² = 7 , where m,n€Z

=> (m+n)(m-n)= 7 ---(1)

now,

case 1:

(m+n)(m-n) = 7×1

m+n = 7

m-n = 1

solving these ,we get

(m,n) = (4,3)

case 2:

(m+n)(m-1) = (-1)(-7)

Now,

m+n = -1

m-n = -7

solving these , we get

(m,n) = (-4,3)

case 3:

(m+n)(m-n) = 1×7

m+n = 1

m-n = 7

Solving these , we get

(m,n) = (4,-3)

case 4:

(m+n)(m-n) = (-7)(-1)

m+n = -7

m-n = -1

solving these, we get

(m,n) = (-4,-3)

Therefore,

Option (D) is correct.

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