Find the area lying above the x-axis and below the parabolic curve y = 4x -x2 A. 8 B. 16 C. 10 2/3 D. 8 1/3
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ANSWER
EXPLANATION
The given right triangle is an isosceles triangle because
This implies that,
From the Pythagoras Theorem,
EXPLANATION
The given right triangle is an isosceles triangle because
This implies that,
From the Pythagoras Theorem,
Our goal here is to somehow "surgically remove" the repeating part of the number, so let's start by putting the original value in a variable and messing around with it a bit.
We'll let . We want to cut the
bit off completely, so let's create the scalpel that'll let us do that. If
, then we can also say that
. Maybe I was lying a bit: the
is our real scalpel here, and
is where we'll be making the cut. Mathematically, a "cut" is almost always shorthand for subtraction, so let's see what our operation (cutting
off of
) leaves us with:
The operation was a success! We can now simply divide either side by 9 to find , which, when reduced by dividing the numerator and denominator by 3, gives us