. For the curves y = 4x3 – 2x5 , find all points at which tangent passes through the origin ? . For the curves y = 4x 3 – 2x 5 , find all points at which tangent passes through the origin ?
. For the curves y = 4x 3 – 2x 5 , find all points at which tangent passes through the origin ?
The equation of the given curve is y = 4x3 − 2x5.
dy/dx = 12x^2 - 10 x^4
Therefore, the slope of the tangent at a point (x, y) is 12x2 − 10x4.
The equation of the tangent at (x, y) is given by,
Y -y = (12x^2 - 10x^4) (X- x) ---(1)
When 0the tangent passes through the origin (0, 0), then X = Y = 0.
Therefore, equation (1) reduces to:
-y=( 12x^2- 10x^4) (-x)
y = 12x^3 - 10x^5
Also, we have
y = 4x^3 - 2x^5
therefore
12x^3 - 10x^5 = 4x^3 - 2x^5
8x^3 - 8x^5 = 0
x^3 - x^5 = 0
x^3 (1-x^2) = 0
x = 0 , plus, minus 1
when x = 0 ,y= 4 (0)^3 - 2(0)^5=0
When x = 1, y = 4 (1)3 − 2 (1)5 = 2.
When x = −1, y = 4 (−1)3 − 2 (−1)5 = −2.
Hence, the required points are (0, 0), (1, 2), and (−1, −2).