Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If (a + b + c) = 6

a2 + b2 + c2 = 32

a3 + b3 + c3 = 189

find the value of abc + 3

Options:

6

8

0

6

Correct Answer:

6

Explanation:

(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)

36 = a2 + b2 + c2 + 2(ab + bc + ca)

36 = 32 + 2(ab + bc + ca)

ab + bc + ca = 2

Now → a3 + b3 + c3 – 3abc = (a + b + c)(a2 + b2 + c2 - ab - bc - ca)

189 – 3abc = 6(32 – 2)

abc = 3

abc + 3 = 6