CAT 2019 Surds and Indices Question (Medium)

Question

The real root of the equation is

Accepted Answer

Step 1 Substitute Let Then Also, So the equation becomes --- Step 2 Solve the quadratic Use quadratic formula So or Reject since So --- Step 3 Solve for x Take log base 2 both sides --- Final Answer A.

CAT 2019

Quantitative

Surds and Indices

Medium

The real root of the equation $2^{6x} + 2^{3x+2} - 21 = 0$ is

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