AP EAMCET Engineering 2012 Solved Paper

Let required equation of line is
y=mx+c ......(i)
Since, angle between y=mx+c
and y=2x+1 is tan‌45°.
∵ tan‌θ=|

m1−m2

1+m1m2

|
⇒ tan‌45°=|

m−2

1+2m

|
⇒ 1=±

m−2

1+2m

⇒ 1+2m=m−2
or 1+2m=−m+2
⇒ m=−3 or 3m=1
⇒ m=−3 or

1

3

On putting m=−3 in Eq. (i), we get
y=−3x+c
Since, it passes through (1,2).
∴ 2=−

1

3

+c⇒c=

7

6

∴ Equation of line is y=−

x

3

+

7

6

⇒ 6y+2x=7
Hence, option (b) is correct.