A²*sin2π +2ab*cos3π/2 +c³*tg2π = a²*0+2ab*0+c³*0=0+0+0=0
a³*ctg270°+b³*tg0° = a³*0+b³*0= 0+0 =0
( 4a - 7b ) + (2a - b) - (5a - 6b) = 4a - 7b + 2a - b - 5a + 6b = a - 2b
(3x+y)(x+y)-4 (x-y)=3x2+3xy+xy+y2-4xy+4y2=3x2+4xy-4xy+5y2=3x2+5y2.
+ - + - +
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0 1 2 3
x ∈ (- ∞ ; 0) ∪ (1 ; 2) ∪ (3 ; + ∞)