CAT Exam  >  CAT Questions  >   How many pairs (m, n) of positive integers s... Start Learning for Free
How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?
Correct answer is '4'. Can you explain this answer?
Verified Answer
How many pairs (m, n) of positive integers satisfy the equation m2 + ...
N2- m2 = 105
(n-m) (n+m) = 1 *105, 3*35, 5*21, 7*15, 15*7, 21 *5, 35*3,105*1.
n – m=1, n+m=105==> n=53, m=52
n – m=3, n+m=35 ==> n=19, m=16
n – m=5, n+m=21 ==>n=13, m=8
n – m=7, n+m=15 ==> n=11, m=4
n – m=15, n+m=7 ==> n=11, m=-4
n – m=21, n+m=5 ==> n=13, m=-8
n – m=35, n+m=3 ==> n=19, m=-16
n – m=105, n+m=1 ==> n=53, m=-52
Since only positive integer values of m and n are required. There are 4 possible solutions.
View all questions of this test
Most Upvoted Answer
How many pairs (m, n) of positive integers satisfy the equation m2 + ...
Solution:

Given equation: m^2 - n^2 = 105

We can factorize the left-hand side of the equation as:

(m + n)(m - n) = 105

Since m and n are positive integers, we know that m + n > m - n. Therefore, we can write:

m + n > m - n ≥ 1

Thus, we have the following possibilities for the values of (m + n) and (m - n):

m + n = 105, m - n = 1
m + n = 35, m - n = 3
m + n = 21, m - n = 5
m + n = 15, m - n = 7

Solving each of these systems of equations, we get:

m = 53, n = 52
m = 19, n = 16
m = 13, n = 12
m = 11, n = 8

Therefore, there are 4 pairs of positive integers (m, n) that satisfy the given equation:

(53, 52), (19, 16), (13, 12), (11, 8)

Hence, the correct answer is 4.
Attention CAT Students!
To make sure you are not studying endlessly, EduRev has designed CAT study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in CAT.
Explore Courses for CAT exam

Top Courses for CAT

How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer?
Question Description
How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? for CAT 2024 is part of CAT preparation. The Question and answers have been prepared according to the CAT exam syllabus. Information about How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? covers all topics & solutions for CAT 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer?.
Solutions for How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? in English & in Hindi are available as part of our courses for CAT. Download more important topics, notes, lectures and mock test series for CAT Exam by signing up for free.
Here you can find the meaning of How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer?, a detailed solution for How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? has been provided alongside types of How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice How many pairs (m, n) of positive integers satisfy the equation m2 + 105 = n2?Correct answer is '4'. Can you explain this answer? tests, examples and also practice CAT tests.
Explore Courses for CAT exam

Top Courses for CAT

Explore Courses
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev