If $f(x)=\frac{2x+5}{x^2+x+5}$, then \

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Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Relations and Functions

Question:

If $f(x)=\frac{2x+5}{x^2+x+5}$, then $f(f(-1))$ is equal to

Options:

$\frac{149}{155}$

$\frac{155}{147}$

$\frac{155}{149}$

$\frac{147}{155}$

Correct Answer:

$\frac{155}{149}$

Explanation:

$f(x)=\frac{2x+5}{x^2+x+5}$

so $f(-1)=\frac{2(-1)+5}{(-1)^2+(-1)+5}=\frac{3}{5}$

so $f(f(-1))=\frac{2×\frac{3}{5}}{\frac{3^2}{5^2}+\frac{3}{5}+5}=\frac{155}{149}$