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Tangent Slope Question?

So here's the problem

Graph the Function of f(x)= square root of x on the interval [0,9]. SHow the secant lines passing throught the point (4,2) and theses values of x : 1, 3, 4,5

ok so far I got that graphed and found the slope of eavh secant line

a. 1/3

b. square root 3 +2

c. Square root 5 - 2

Now the problem where im stuck is estimate the slope of the tangent to the curve at the point (4,2)

i don't understand how im suppose to get the answer. Please don't use derivatives. Thank you so much for the help

Update:

forget the 4 i put in for the extra values that was a mistake just 1,3,5

1 Answer

Relevance
  • Joerg
    Lv 6
    9 years ago

    If I understand this right, there are three lines

    to be found:

    a) passing through (1,?) and (4,2)

    b) passing through (3,?) and (4,2)

    c) passing through (5,?) and (4,2)

    They have the following formulae:

    a) y=2/3*x-2/3

    b) y=2*x-6

    c) y=-2*x+10

    The factor of x is the respective slope:

    for a)=2/3

    for b)=2

    for c)=-2

    To estimate the slope of the tangent at (4,2)

    your aren't too far away with the first slope

    which is 2/3.

    It appears to be a bit too steep.

    You could try to lower it a bit and find

    the equation of the tangent line either

    passing (4,2) or passing nearby. This way

    you could judge from comparing the slopes

    visually.

    E.g.try:

    y=1/3*x+2/3

    y=1/4*x+1

    It's an estimate, not an exact value.

    Hope it helps.

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