25b²-90b+81-50b²+90b= -25b²+81= -25*21+81= -525+81= -444
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Verified answer
(5b-9)²-10b(5b-9)=81-25b^281-25(√21)^2=81-25*21=81-525=-444
Verified answer
25b²-90b+81-50b²+90b= -25b²+81= -25*21+81= -525+81= -444