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2010-02-26T12:04:05+01:00
2(2x-4y)-2x(x+y)=
4x-8y-2x²-2xy=4*2-8*3-2*2²-2*2*3=8-24-8-12=-36
x=2 y=3

2x(x+7) + 2[2x+3(y-2)]=2x²+14x+2(2x+3y-6)=2x²+14x+4x+6y-12=
2x²+18x+6y-12=2*5²+18*5+6*2-12=50+90+12-12=140
x=5 y=2

a. (3x−4)²=9x²-24x+16
b. (2p+3r)²=4p²+12pr+9r²
c. (r-2x)(r+2x)=r²-4x²
d. (3p-2m)(2p+2m)=6p²-4mp+6mp-4m²=6p²+2mp-4m²

a. 4−4x+x²=(x-2)²
b. 25h²+30hk+3k²=(5h+3k)²-3k²
c. 36d²−9c²=6d-3c)(6d+3c)
d. 100r²−20rtu+t² u²=(10r-tu)²