Answer:
Below in bold.
Step-by-step explanation:
1) ( a^2 + b^2 = (a + b)^2 - 2ab
= 29 - 2(6)
= 29-12
= 17.
2). (x - y)^2 = x^2 + y^2 - 2xy
so 20 = 18 - 2xy
2xy = 18-20 = -2
xy = -1.
3). 1/x + x = 7
(1/ x + x)^2 = 1/x^2 + x^2 +x/x + x/x
= 1/x^2 + x^2 + 2
But(1/x + x)^2 = 7^2 = 49
so 1/x^2 + x^2 + 2 = 49
so 1/x^2 + x^2 = 49 - 2 = 47.
