Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Question:

The equation of tangent line to $y = 2x^2+7$, which is parallel to the line $4x-y+3 = 0$ is

Options:

$4x-y+7=0$

$4x-y+3=0$

$4x-y+5=0$

$4x-y+1=0$

Correct Answer:

$4x-y+5=0$

Explanation:

The correct answer is Option (3) → $4x-y+5=0$

Given curve: $y = 2x^2 + 7$

Given line: $4x - y + 3 = 0 \Rightarrow y = 4x + 3$

Slope of given line: $m = 4$

Slope of tangent to curve: $\frac{dy}{dx} = 4x$

Set equal to 4: $4x = 4 \Rightarrow x = 1$

Corresponding $y$ on curve: $y = 2(1)^2 + 7 = 9$

Equation of tangent: $y - 9 = 4(x - 1) \Rightarrow y = 4x + 5$