Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If a + b = \(\frac{3}{4}\) and ab = \(\frac{1}{8}\), then

find a4 + b4 + ab3 + ba3.

Options:

\(\frac{27}{128}\)

\(\frac{9}{256}\)

\(\frac{27}{256}\)

\(\frac{9}{64}\)

Correct Answer:

\(\frac{27}{256}\)

Explanation:

a + b = \(\frac{3}{4}\)

Squaring both sides

a2 + b2 + 2ab = \(\frac{9}{16}\)

a2 + b2 = \(\frac{9}{16}\) - 2 × \(\frac{1}{8}\)

a2 + b2 = \(\frac{5}{16}\)

Squaring both sides again in equation

a4 + b4 = \(\frac{25}{256}\) - 2a2b2 

a4 + b4 = \(\frac{25}{256}\) - 2 × \(\frac{1}{64}\)

a4 + b4 = \(\frac{17}{256}\)

⇒ Put the value in below equation

⇒ a4 + b4 + ab (a2 + b2) = \(\frac{17}{256}\) + \(\frac{5}{128}\) = \(\frac{27}{256}\)