Which quadratic function best fits this data?
1 answer:
The data has a peak at x=5, so we expect it to be modeled with a parabola that opens downward. That is the x² coefficient will be negative.
For x=1, the third choice gives a better approximation to (x, y) = (1, 32) than does the first choice. It is appropriate to choose
... y = -11.41x²+154.42x-143.9
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The quadratic regression function of a graphing calculator confirms this choice.
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Since the divisor is 2 digits, start by looking at the first 2 digits of the dividend. Those are 44, so you're dividing 44 by 15 at the first step. The quotient digit is the largest integer that gives a value less than or equal to the dividend (44) when multiplied by the divisor (15). For the first step, that digit is 2.
To find the new divisor, subtract the product of the divisor and the quotient digit (2·15=30) and bring down the next digit of the original dividend. Now, you have a dividend of 147 and a divisor of 15. Repeat the process as above.
The decimal point location in the answer can be found a number of ways. The simpliest is to put it above the decimal point in the dividend. (When the divisor is not an integer, multiply or divide both divisor and dividend by the same power of 10 until it is.)
