Below are two different functions, f(x) and g(x). What can be determined about their slopes? f(x) Dawn writes 800 pages in 80 da
1 answer:
Given function f(x) which is described by "<span>Dawn writes 800 pages in 80 days".
From this function we can notice that Dawn writes 0 pages in 0 days, (i.e. the initial point of the function is point (0, 0).
Recall that the slope, m, of a line passing through points:
and 
is given by
Function f(x) passes through points (0, 0) and (80, 800).
Thus the slope of function f(x) is given by
Give function g(x), passing through points (2, -6) and (4, 12), the slope is given by
It can be seen that the slope of f(x) and the slope of g(x) are close.
</span>
From this function we can notice that Dawn writes 0 pages in 0 days, (i.e. the initial point of the function is point (0, 0).
Recall that the slope, m, of a line passing through points:
is given by
Function f(x) passes through points (0, 0) and (80, 800).
Thus the slope of function f(x) is given by
Give function g(x), passing through points (2, -6) and (4, 12), the slope is given by
It can be seen that the slope of f(x) and the slope of g(x) are close.
</span>
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The first step in any problem is to look at what you are given. When solving systems of linear equations, it is often helpful to eliminate one or more of the variables by adding or subtracting a multiple of one equation with a multiple of another. It is convenient when at least one of the multipliers is 1.
Here, we can cancel the y-terms in the 2nd and 3rd equations simply by adding them together. This gives
... (5x +y -4z) +(-3x -y +5z) = (41) +(-45)
... 2x +z = -4 . . . . simplified
Likewise, we can add 3 times the second equation to the first to cancel y in that sum.
... 3(5x +y -4z) +(2x -3y +z) = 3(41) + (-1)
...15x +3y -12z +2x -3y +z = 123 -1
...17x -11z = 122 . . . . simplified
Now that we have 2 equations in x and z, we can go through the same process. We observe that the coefficient of z is +1 in the first equation and -11 in the second. The means we can cancel the z terms by adding 11 times the first equation to the second:
... 11(2x +z) +(17x -11z) = 11(-4) +122
...22x +17x = 78 . . . . . . simplify a little bit
... x = 78/39 = 2 . . . . . . divide by 39
From above, we find
... z = -4 -2x = -4 -2·2 = -8
... y = 41 -5x +4z = 41-5(2) +4(-8) = 41 -42 = -1
The solution is (x, y, z) = (2, -1, -8).
_____
The method of elimination used here will vary with the system of equations. If you want to employ a consistent method, you can use Cramer's Rule, Gaussian elimination, or matrix methods. Since you apparently don't mind help from technology, learning to do this on your graphing calculator can also be a good idea.
