Let$${f}{\left({\mathtt{x}}\right)} = {{\mathtt{x}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}$$,the straight line L intersects the graph y=f(x) at M and N.The slope and the y-intercept of L are m and 1 respectively.
1)Express the y -coordinate of the mid-point MN in terms of m.
thank you
We can write L as
y = mx + 1
So, let us find the intersection of these two functions
mx + 1 = x^2 - 2x + 2
X^2 - 2x + 2 - mx - 1 = 0
x^2 -(2+m)x + 1 = 0
So, using the quadratic formula, we have
x = [( 2 + m) ± √[(2+m)^2 - 4]/2 = [(2 +m) ±√(m^2 + 2m)] /2
So, the y coordinates of M, N lie on line L and are given by
y1 = m[(2+m) + √(m^2 + 2m)] /2 + 1 and
y2 = m[(2+m) - √(m^2 + 2m)] /2 + 1
Adding these two we have
[m[(2+m) + √(m^2 + 2m)] /2 + 1 ] + [ m[(2+m) - √(m^2 + 2m)] /2 + 1 ] =
[m(2 + m) + 2]
And dividing this by 2, we get the midpoint =
(m/2)(2 + m) + 1 =
(1/2)m^2 + m + 1
We can write L as
y = mx + 1
So, let us find the intersection of these two functions
mx + 1 = x^2 - 2x + 2
X^2 - 2x + 2 - mx - 1 = 0
x^2 -(2+m)x + 1 = 0
So, using the quadratic formula, we have
x = [( 2 + m) ± √[(2+m)^2 - 4]/2 = [(2 +m) ±√(m^2 + 2m)] /2
So, the y coordinates of M, N lie on line L and are given by
y1 = m[(2+m) + √(m^2 + 2m)] /2 + 1 and
y2 = m[(2+m) - √(m^2 + 2m)] /2 + 1
Adding these two we have
[m[(2+m) + √(m^2 + 2m)] /2 + 1 ] + [ m[(2+m) - √(m^2 + 2m)] /2 + 1 ] =
[m(2 + m) + 2]
And dividing this by 2, we get the midpoint =
(m/2)(2 + m) + 1 =
(1/2)m^2 + m + 1