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a) 5y²-3(y+1)(y-1)=2y²+3
5y²-3(y²-1)=2y²+3
5y²-3y²+3=2y²+3
5y²-3y²-2y²=3-3
0=0 (jest tożsamością)
b) 7(z²-2)-4(z+3)(z-3)=3z²+22
7z²-14-4(z²-9)=3z²+22
7z²-14-4z²+36=3z²+22
7z²-4z²-3z²=22+14-36
0=0 (jest tożsamością)
c) 10(a²-15)-12(a-4)(a+4)=42-2a²
10a²-150-12(a²-16)=42-2a²
10a²-150-12a²+192=42-2a²
10a²-12a²+2a²=42+150-192
0=0 (jest tożsamością)
zadanie 2
a)97²=(100-3)²=10000-600+9=9409
b)41²=(40+1)²=1600+80+1=2401
c)52²=(50+2)²=2500+200+4=2704
d)81²=(80+1)²=6400+160+1=6561
e)98²=(100-2)²=10000-400+4=9604
f)49²=(50-1)²=2500-100+1=2401
g)199*201=(200-1)(200+1)=200²-1²=39999
h)72*68=(70+2)(70-2)=70²-2²=4896
i)55²-45²=(50+5)²-(40+5)²=(2500+500+25)-(1600+400+25)=2500+500+25-1600-400-25=1000