Đáp án:
Giải thích các bước giải:
Bài 1
a, -|-12|-(-5+|-4|-12)+(-9)= -12-(-5+4-12)-9=-12+5-4+12-9=-8
b)-(-15)-(-3+7-8)-|-5|=15-(-4)-5=15+4-5=14
c)|11-13|-(-12+20-8-10)= 2-(-10)=2+10=12
d)-|-5+3-7|-|-5+7|= -9-2=-11
e)13-[(5-(4-5)+6]-[3-(2-7)]=13-(6+6)-8=-7
Bài 2
a)3-(17-x)=289-(36+289)
⇔ 3-17+x=-36
⇔-14+x=-36
⇔x=-22
b)25-(x+5)=-415-(15-415)
⇔25-x-5=-15
⇔-x=-35
⇔x=35
c)3-|x+1|=-5
⇔|x+1|=3+5
⇔|x+1|=8
⇔\(\left[ \begin{array}{l}x+1=8\\x+1=-8\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=7\\x=-9\end{array} \right.\)
d)12-|x+3|=10
⇔|x+3|=12-10
⇔|x+3|=2
⇔\(\left[ \begin{array}{l}x+3=2\\x+3=-2\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-1\\x=-5\end{array} \right.\)
g)|x+5|-5=4-(-3)
⇔|x+5|=12
⇔\(\left[ \begin{array}{l}x+5=12\\x+5=-12\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=7\\x=-17\end{array} \right.\)
Bài 3
a,1-2+3-4+5-...+2019-2020
=-(2020-2019+...+4-3+2-1)
=-(1+...+1+1)(1010 số 1)
=-1010
