Chứng minh các đẳng thức sau: a) 2(x² + y²) = (x + y²) + ( x- y)²
b) (a + b)² - (a-b) (a+ b) = 2b ( a+ b )
c) x² + y² = ( x+ y²) - 2xy

The box plots show the distributions of the numbers of words per line in an essay printed in two different fonts.which measure of center would be best to compare the data sets? the median is the best measure because both distributions are left-skewed.the mean is the best measure because both distributions are left-skewed.the median is the best measure because both distributions are symmetric.the mean is the best measure because both distributions are symmetric