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2009-12-01T16:39:29+01:00
B) -(2a-5)²=(1-2a)(1+2a)
-(4a²-20a+25) = 1-4a²
-4a²+20a-25= 1-4a²
-4a²+20a+4a² = 1+25
20a= 26 /÷20
a= 26/20
a= 1 4/20
a= 1 ⅕


a) (x-5)²=x²=15
x²-10x+25=x²= 15
x²-10x-x²= 15-25
-10x= -10 /÷ (-10)
x=1