Q. Determine the following limit in simplest form. If the limit is infinite, state that the limit does not exist (DNE).x→∞lim6x3+9327x12−23x8Answer:
Identify Powers of x: Identify the highest power of x in both the numerator and the denominator.In the numerator, the highest power of x inside the cube root is x12, and in the denominator, the highest power of x is x3.
Factor Out Highest Power: Factor out the highest power of x from the cube root in the numerator.Since the highest power of x inside the cube root is x12, we can factor out x4 from the cube root (because (x4)3=x12).The expression becomes:limx→∞(3x12(27−23/x4))/(6x3+9)
Simplify Cube Root: Simplify the cube root in the numerator.The cube root of x12 is x4, so the expression simplifies to:x→∞lim⎝⎛6x3+9x4⋅327−x423⎠⎞
Divide by x3: Divide every term by x3, the highest power of x in the denominator.This gives us:limx→∞(x3x4⋅327−x423)/(6+x39)
Cancel x3 in Numerator: Simplify the expression by canceling out x3 from x4 in the numerator.This simplifies to:limx→∞(6+x39x⋅327−x423)
Evaluate Limit at Infinity: Evaluate the limit as x approaches infinity. As x approaches infinity, x423 approaches 0 and x39 approaches 0. The expression simplifies to: limx→∞(6x⋅327)
Calculate Cube Root: Calculate the cube root of 27 and simplify the expression.The cube root of 27 is 3, so the expression simplifies to:limx→∞63x
Divide by 6: Simplify the expression by dividing 3x by 6. This simplifies to: limx→∞(2x)
Evaluate Limit at Infinity: Evaluate the limit as x approaches infinity. As x approaches infinity, 2x also approaches infinity. Therefore, the limit does not exist (DNE).
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