Question

a + b + c = 9, a^2 + b^2 + c^2 = 29 হলে ab + ba + ca = কত?

Options

1

26

Correct Answer
2

28

Correct Answer
3

20

Correct Answer
4

25

Correct Answer

Explanation

আমরা জানি, (a+b+c)^2 = a^2+b^2+c^2 + 2(ab+bc+ca)। বা, 9^2 = 29 + 2(ab+bc+ca)। বা, 81-29 = 2(ab+bc+ca)। বা, 52 = 2(ab+bc+ca)। বা, ab+bc+ca = 26।

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