Which is not a property of mathematical proofs?
Conclusion has nothing to do with math
it is for writeing.
Part I
We have the size of the sheet of cardboard and we'll use the variable "x" to represent the length of the cuts. For any given cut, the available distance is reduced by twice the length of the cut. So we can create the following equations for length, width, and height.
width: w = 12 - 2x
length: l = 18 - 2x
height: h = x
Part II
v = l * w * h
v = (18 - 2x)(12 - 2x)x
v = (216 - 36x - 24x + 4x^2)x
v = (216 - 60x + 4x^2)x
v = 216x - 60x^2 + 4x^3
v = 4x^3 - 60x^2 + 216x
Part III
The length of the cut has to be greater than 0 and less than half the length of the smallest dimension of the cardboard (after all, there has to be something left over after cutting out the corners). So 0 < x < 6
Let's try to figure out an x that gives a volume of 224 in^3. Since this is high school math, it's unlikely that you've been taught how to handle cubic equations, so let's instead look at integer values of x. If we use a value of 1, we get a volume of:
v = 4x^3 - 60x^2 + 216x
v = 4*1^3 - 60*1^2 + 216*1
v = 4*1 - 60*1 + 216
v = 4 - 60 + 216
v = 160
Too small, so let's try 2.
v = 4x^3 - 60x^2 + 216x
v = 4*2^3 - 60*2^2 + 216*2
v = 4*8 - 60*4 + 216*2
v = 32 - 240 + 432
v = 224
And that's the desired volume.
So let's choose a value of x=2.
Reason?
It meets the inequality of 0 < x < 6 and it also gives the desired volume of 224 cubic inches.
To evaluate the radius of the cone we proceed as follows:
V=1/3 πr²h
plugging in the values, v=88π, h=8 ft
step 1
88π1/3πr²(8)
step 2
88π=8/3πr²
step 3
divide both sides by π
88=8/3r²
multiply both sides by 3/(8)
88(3/8)=r²
step 4
simplify
33=r²
step 5
get the square root
r=√33
Thus the mistake that Fatima made was:
<span> In step 3, Fatima did not multiply 88 by the reciprocal of 8/3 </span>
Solve your system of equations.
2x+y=1;4x+2y=−1
Solve 2x+y=1 for y:
2x+y+−2x=1+−2x(Add -2x to both sides)
y=−2x+1
Substitute (−2x+1) for y in 4x+2y=−1:
4x+2y=−1
4x+2(−2x+1)=−1
2=−1(Simplify both sides of the equation)
2+−2=−1+−2(Add -2 to both sides)
0=−3
Answer: No solution. C)
