Explanation:
Hey there!
The equation of line which passes through the point (1,2) is (y-2) = m1(x-1)............(i)
The another given equation is y= 2x + 3.........(ii)
Comparing the equation (ii) with y= mx+c we get;
Slope (m2)= 2.
As per the condition of perpendicular lines, m1*m2 = -1.
m1*2 = -1
Therefore, m1 = -1/2.
Keeping the value of m1 in equation (i) we get;
(y-2) = -1/2(x-1)
y - 2 = -1/2x +1/2
y = -1/2 X + 1/2 + 2
Therefore, the required equation is y = -1/2 X + 5/2.
Hope it helps!