1.
5.15² - 2*5.15*3.15+3.15² = (5.15-3.15)² = 2² = 4
7.25² - 2.75² (7.25-2.75)(7.25+2.75) 4.5*10 45
2.
a) (x+1)² -(x-2)(x+4)=x²+2x+1-(x²-2x+4x-8)=x²+2x+1-x²-2x+8=9
б) (a+b)(a-b)(a²+b²)=(a²-b²)(a²+b²)=a⁴-b⁴
3.
( 5 - 1 ) : 3 = ( 5 + 1 ) * x-2y =
(2x-4y 2y-x ) x-2y (2(x-2y) x-2y) 3
= 5+2 * x-2y = 7 = 1 ¹/₆
2(x-2y) 3 6