已知,求代数式的值.
计算:
(本小题6分)计算:42°30′÷2 + 16°23′×5
(本小题每题6分,共12分)解方程:(1) 3x +5 = 4x + 1 (2) -1=
(本小题每题6分,共12分)(1)化简:x+7x-5x (2)先化简再求值: a2b-5ac-(3a2c-a2b)+(5ac-4a2c)其中a=-1,b=2,c=3
(本小题每题6分,共12分)计算:(1) -8+4÷(-2) (2) (+-)×12+(-2)3