①(-49)-(+91)-(-5)+(-9)=-49-91+5-9=-144;
② (-
5
8 )×(-4 ) 2 -0.25×(-5)×(-4 ) 3 = (-
5
8 )×16 -0.25×(-5)×(-64) =-10-80=-90;
③(-48)÷6-(-25)×4=-8+100=92;
④5a 2-[a 2+(5a 2-2a)-2(a 2-3a)]=5a 2-[a 2+5a 2-2a-2a 2+6a]=5a 2-a 2-5a 2+2a+2a 2-6a=a 2-4;
①(-49)-(+91)-(-5)+(-9)=-49-91+5-9=-144;
② (-
5
8 )×(-4 ) 2 -0.25×(-5)×(-4 ) 3 = (-
5
8 )×16 -0.25×(-5)×(-64) =-10-80=-90;
③(-48)÷6-(-25)×4=-8+100=92;
④5a 2-[a 2+(5a 2-2a)-2(a 2-3a)]=5a 2-[a 2+5a 2-2a-2a 2+6a]=5a 2-a 2-5a 2+2a+2a 2-6a=a 2-4;