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যদি $a + b = 7$ এবং $a - b = 3$ হয়, তবে $a^2 - b^2$-এর মান কত?

A$14$
B$10$
C$21$
D$28$
Answer & Solution
Correct answer: C. $21$
বর্গের অন্তরের অভেদ $a^2 - b^2 = (a+b)(a-b) = 7 \times 3 = 21$ ব্যবহার করুন।
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