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2009-09-06T14:53:11+02:00
A) (√5 - √3)² - (√5+√3)²= 5-2√15 +3-(5+2√15+3)= -2√15-2√15=-4√15
b) (√3-2)³-(√3+2)³= 3√3-3*3*2 + 3*√3*4- 8 - (3√3+3*3*2+ 3*√3*4 +8)=
= 3√3-18+12√3-8-(3√3+18+12√3+8= 15√3-26-15√3-26= -52
c)(2x-1)²-(x-2)²=2x*2x-2*2x*1+1-(x²-2*2*x+4)= 4x²-4x+1-(x²-4x +4)=
= 3x²-3=3(x-1)(x+1)
d)(x+2)²-3(x+1)(x-7)= x²+4x+4-3(x2-7x+x-7)=x²+4x+4-3x²+21x-3x+21= -2x²+22x+25