
Hi sushi 88, can I solve the ‘show’ question like this in the picture? Thanks
Hi sushi 88, can I solve the ‘show’ question like this in the picture? Thanks
To show that the line is tangent to the quadratic function,
For intersection, you have to equate the two expressions but how many points of intersections is still not clear at this stage, so you have to write:
To find points of intersection,
2x2 -5x – 10 = -x -12
………………… your working is correct here
x2 -2x + 1 = 0 (resulting quadratic)
(x-1)(x-1) = 0 => x = 1 , y = -13
Hence (1,-13) is the only point of intersection.
Next, you can write to determine if b2 – 4ac = 0 for x2 -2x + 1 = 0 ( resulting quadratic) to confirm the line is tangent to the curve,
Since a = 1, b = -2, c = 1 => (-2)2 – 4(1)(1) = 4 – 4 = 0
Hence line y = -x -12 is tangent to the curve y = 2x2 -5x – 10
i understand your explanation :), please correct my other questions too. thanks very much
I have to scoot off for a few hours, will review your other questions later tonight.
thank you.