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Calculus

GATE CSE 2021 Set 1 · Q20

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Consider the following expression. lim⁡x→−32x+22−4x+3\lim_{x \to -3} \frac{\sqrt{2x+22}-4}{x+3} The value of the above expression (rounded to 2 decimal places) is ________.

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Official answer: 0.25 (±0)

Calculus

Evaluating the limit directly by substituting x=−3x = -3 gives an indeterminate form of 00\frac{0}{0}:

2(−3)+22−4−3+3=16−40=00\frac{\sqrt{2(-3)+22}-4}{-3+3} = \frac{\sqrt{16}-4}{0} = \frac{0}{0}

Applying L'Hôpital's Rule, we differentiate the numerator and the denominator with respect to xx:

lim⁡x→−3ddx(2x+22−4)ddx(x+3)=lim⁡x→−3122x+22⋅21=lim⁡x→−312x+22\lim_{x \to -3} \frac{\frac{d}{dx}(\sqrt{2x+22}-4)}{\frac{d}{dx}(x+3)} = \lim_{x \to -3} \frac{\frac{1}{2\sqrt{2x+22}} \cdot 2}{1} = \lim_{x \to -3} \frac{1}{\sqrt{2x+22}}

Substituting x=−3x = -3:

12(−3)+22=116=14=0.25\frac{1}{\sqrt{2(-3)+22}} = \frac{1}{\sqrt{16}} = \frac{1}{4} = 0.25

Thus, the value of the expression is 0.25.

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This Calculus previous year question is Q20 of the GATE CSE 2021 Set 1 paper. Find more GATE CSE PYQs on Calculus in Engineering Mathematics, or browse all GATE CSE PYQs.

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Calculus in GATE CSE

Calculus has 40 GATE CSE PYQs across 25 papers from 2011 to 2026. 11 of them are 1-mark NAT questions like this one, and it is the only one in GATE CSE 2021 Set 1.

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GateAI solution cardGATE CSE 2021 Set 1 · Q20 · NAT

Consider the following expression. limx → -3 √(2x+22)-4x+3 The value of the above expression (rounded to 2 decimal places) is …

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