50 + 50 = 100, 500 + 5000 = 5500, 500000000 + 987687987.0987657890-789 + 98 =? Simple calculation

Use death to calculate, as long as not to calculate death. This problem only needs to calculate the following part of 50000000000 +
987687987.0987657890-789+98
=987687987.0987657890-（789-98）
=987687987.0987657890-691
=987687296.098765789
The final addition of 500000000 is 50987687296.098765789

The sum of 501 + 502 + 503 + 504 + 505 + 506 + 507 is 3528, and the sum multiplied by the middle number is 35

504×7=3528

The range of data 501.502.503.504.505.506.507.508.509 is
The variance is

Range is the largest number minus the smallest number
509-501=8
variance
If the average of x1, X2, x3.xn is m
Then variance s ^ 2 = 1 / n [(x1-m) ^ 2 + (x2-m) ^ 2 +. + (xn-m) ^ 2]
Variance is the mean deviation from the square, which is called standard deviation or mean square deviation,
The variance is 60
In fact, the variance is not calculated by my hand, but by the DEVSQ function of Excel

Teacher he gave the students a question: when x = 2013, y = 2014, find the value of [2x (x square, y-xy & # 178;) + XY (2xy-x & # 178;)] / X & # 178; y. after the question, Xiao Ming said: "the condition given by the teacher, y = 2 014, is redundant." Wang Guang said: "if you don't give this condition, you can't find the result, so it's not redundant." who do you think makes sense? Why?

[2x (x squared y-xy & # 178;) + XY (2xy-x & # 178;)] / / X & # 178; y
=(2x³y-2x²y²+2x²y²-x³y)÷x²y
=x³y÷x²y
=x
Because the simplified result is only related to x, what Xiao Ming said is reasonable

50 + 50 = 100, 500 + 5000 = 5500, 500000000 + 987687987.0987657890-789 + 98 =? Simple calculation