Question

当a=-3/2时,求代数式15a^2-{-4a^2+[5a-8a^2-(2a^2-a)+9a^2]-3a}

Answer 1

15a^2-{-4a^2+[5a-8a^2-(2a^2-a)+9a^2]-3a}

=15a^2-{-4a^2+[5a-8a^2-2a^2+a+9a^2]-3a}

=15a^2-{-4a^2+[6a-a^2]-3a}

=15a^2-{-4a^2+6a-a^2-3a}

=15a^2-{-5a^2+3a}

=15a^2+5a^2-3a

=20a^2-3a

=20×（-3/2）²-3×(-3/2)

=20×9/4+9/2

=45+9/2

=99/2