Diego is building a kitchen table and a coffee table. The legs of a kitchen table must be twice the height of a coffee table and there are 4 legs on each table. He writes the expression 4(2x) + 4(x) to model his building plans. What does 2x represent?
2x represents the height of one kitchen table leg. 2x represents the total height of all four kitchen table legs. 2x represents the height of one coffee table leg.<span> 2x represents the total height of all four coffee table legs.</span>
10.25 + 2.00 = 12.25...cost of pizza and soda
12.25 - 1.50x = 4.75....with x being the number of touchdowns
-1.50x = 4.75 - 12.25...I subtracted 12.25 from both sides
-1.50x = - 7.50...now divide both sides by -1.50
x = -7.50 / -1.50
x = 6......They would have to score 6 touchdowns
Explanation:
It helps to understand the process of multiplying the binomials. Consider the simple case ...
(x +a)(x +b)
The product is ...
(x +a)(x +b) = x² +(a+b)x + ab
If the <em>constant</em> term (ab) is <em>negative</em>, the signs of (a) and (b) are <em>different</em>.
If the constant term (ab) is <em>positive</em>, the signs of (a) and (b) will both match the sign of the coefficient of the linear term (a+b).
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Of course, the sum (a+b) will have the sign of the (a) or (b) value with the largest magnitude, so when the signs of (a) and (b) are different, the factor with the largest magnitude will have the sign of (a+b), the x-coefficient.
<u>Example</u>:
x² -x -6
-6 tells you the factors will have different signs. -x tells you the one with the largest magnitude will be negative.
-6 = -6×1 = -3×2 = ... (other factor pairs have a negative factor with a smaller magnitude)
The sums of these factor pairs are -5 and -1. We want the factor pair that has a sum of -1, the coefficient of x in the trinomial.
x² -x -6 = (x -3)(x +2)
We performed the following operations:
![f(x)=\sqrt[3]{x}\mapsto g(x)=2\sqrt[3]{x}=2f(x)](https://tex.z-dn.net/?f=f%28x%29%3D%5Csqrt%5B3%5D%7Bx%7D%5Cmapsto%20g%28x%29%3D2%5Csqrt%5B3%5D%7Bx%7D%3D2f%28x%29)
If you multiply the parent function by a constant, you get a vertical stretch if the constant is greater than 1, a vertical compression if the constant is between 0 and 1. In this case the constant is 2, so we have a vertical stretch.
![g(x)=2\sqrt[3]{x}\mapsto h(x)=-2\sqrt[3]{x}=-g(x)](https://tex.z-dn.net/?f=g%28x%29%3D2%5Csqrt%5B3%5D%7Bx%7D%5Cmapsto%20h%28x%29%3D-2%5Csqrt%5B3%5D%7Bx%7D%3D-g%28x%29)
If you change the sign of a function, you reflect its graph across the x axis.
![h(x)=-2\sqrt[3]{x}\mapsto m(x)=-2\sqrt[3]{x}-1=h(x)-1](https://tex.z-dn.net/?f=h%28x%29%3D-2%5Csqrt%5B3%5D%7Bx%7D%5Cmapsto%20m%28x%29%3D-2%5Csqrt%5B3%5D%7Bx%7D-1%3Dh%28x%29-1)
If you add a constant to a function, you translate its graph vertically. If the constant is positive, you translate upwards, otherwise you translate downwards. In this case, the constant is -1, so you translate 1 unit down.
