The equation of the tangent to the curve y = x2 – 2x + 7, which is parallel to the line 2x – y + 9 = 0, is
Answer & explanation
Correct answer: option 1
y = x2 – 2x +7
On differentiating with respect to x, we get
$\frac{dy}{dx}=2x-2$ ....(i)
equation of the line 2x – y + 9 = 0
⇒ y = 2x + 9 It's in the form of y = mx + c
So, ∴ Slope of the line = 2 ....(ii)
If a tangent is parallel to the line 2x – y + 9 = 0, then slope of the tangent is equal to slope of the line.
∴ 2 = 2x - 2 → from eq. (i) & (ii)
2 + 2 = 2x
$4 = 2x ⇒ \frac{4}{2}=x=2$
$y=x^2-2x+7$
y = 4 - 4 + 7 = 7
Thus equation of the tangent passing through (2,7) is given by,
$y - y_1 = m (x-x_1)$
$y - 7 = 2 (x - 2)$
$⇒ y-2x-3=0$
Required equation of tangent parallel to line 2x – y + 9 = 0 is
y – 2x – 3 = 0
-2x + y - 3 = 0
2x - y + 3 = 0
Option 1 is correct.