21 - 16.75 is 4.25. Do the problem on a calculator and you'll get it.
You can focus on the two sub-triangles ABC and ACD
We know that they are both right triangles, because we're given that AC and BD are perpendicular.
The sides AB and AD are the hypothenuses of these triangles, so we know their length through the pythagorean theorem:
But since we're given 
, the expressions for AD and AB are actually the same expression. This proves that AD=AB, and thus that the triangle is isosceles.
Answer:
42.1% of variation in the response is explained by the regression line
Step-by-step explanation:
Correlation coefficient is a measure which tells us that how strongly are two variables under study are linearly related to each other i.e correlation coefficient gives the strength of linear association between the variables.
If the magnitude of correlation coefficient is closer to 1, it indicates a strong linear relationship. If the magnitude of correlation coefficient is closer to 0, it indicates a weak linear relationship.
There is another variable known as "Coefficient of Determination", which is equal to square of Correlation Coefficient. Coefficient of Determination tells us that what percentage of variation in the response of the study can be explained by the regression line.
This means, for this question we need to calculate the Coefficient of Determination.
Correlation coefficient = r = 0.649
Coefficient of Determination = R = r² = (0.649)²= 0.421 = 42.1 %
This means that 42.1% of variation in the response is explained by the regression line.
Answer: let's say x = 1
16 x 1 =16
16+20=36
36x1/2=18
Step-by-step explanation:
