Given x = y = 8, xy = 12, find ①x^2+xy^2 ②x^2-xy+y^2 ③x-y ④(x-y)^2 Write a process OK

Given x = y = 8, xy = 12, find ①x^2+xy^2 ②x^2-xy+y^2 ③x-y ④(x-y)^2 Write a process OK

Have you studied equations?
x-y=8
xy=12
therefore

If x ^ + y ^ = 25 and xy = 12, then x + y =?,

It's the square of X and y!
( x+y)^=x^+y^+2xy
X ^ + y ^ = 25, xy = 12
( x+y)^=25+24=49
X + y = plus or minus 7

Let x, Y > 0, and X + y = 1. The following inequality is correct: XY ≥ 1 / 4 x ^ 2 + y ^ 2 ≤ 1 / 2 1 / x + 9 / Y ≥ 12 1 / x + 9 / Y ≥ 16
We need to explain it in detail

This is a good judgment! The special value method takes x = 1 / 3, y = 2 / 3 to know the first and second error, and the third error can be known by replacing it. The correct one is ≥ 16