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junior college 2 | H2 Maths
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Jennifer
Jennifer

junior college 2 chevron_right H2 Maths

Pls help w q1&2 pls!!

Date Posted: 6 years ago
Views: 375

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Tham KY
Tham Ky's answer
6052 answers (Tutor Details)
1st
Q1...
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Q2...
Jennifer
Jennifer
6 years ago
Why do we have to sub 2 into 1?
I only stop at y=1-x
Tham KY
Tham KY
6 years ago
Tangent parallel to x-axis is a perfect horizontal line, y=1-x is not a horizontal line. Must be in the format of y=k where k is a constant.
Jennifer
Jennifer
6 years ago
So this is an unusual case where we have to sub back into the original eqn?
Tham KY
Tham KY
6 years ago
It is unusual if you don't!
dy/dx is just a gradient, you need to form an equation of a straight line for a tangent.
Just that this gradient depends not only on x but also y, make it looks like a straight line eqn.
Tham KY
Tham KY
6 years ago
The y=1-x is the result of dy/dx=0, meaning it is the result that cause the gradient to be zero. Not the eqn of the straight line tangent.
Jennifer
Jennifer
6 years ago
Oh okay.. cos Usually when sub dydx =0 will get the eqn of tangent directly, didnt know have to sub back..
Tham KY
Tham KY
6 years ago
Usually after sub dy/dx=0, we found x=constant. This x is the x-coordinate on the curve which has the gradient wanted (in this case, the gradient is zero) then find the corresponding y-coord. Finally we do y-y1=gradient*(x-x1) for the tangent...

This special case gives a linear eqn as the solution to dy/dx, makes us confused that was the eqn of the tangent...

Wish you understand my explanation.
Jennifer
Jennifer
6 years ago
Ohh alright thank you!