1) 3.(-4)2+2.(-5)-20
= 3.16+(-10)-20
= 48+(-10)-20
= 38-20
= 18
2) 5.(-3)2-14.(-8)+(-40)
= 5.9-(-112)+(-40)
= 45-(-112)+(-40)
= 157+(-40)
= 117
3) 31-[26-(209+35)]
= 31-[26-244]
= 31-[-218]
= 249
Tk mk nhé!Thank you very much!
mk làm câu 3 nha!!!
\(31-\left[26-\left(209+35\right)\right]\)
\(=31-\left[26-209-35\right]\)
\(=31-26+209+35\)
\(=\left(31+209\right)+\left(-26+35\right)\)
\(=240+9\)
\(=249\)
chúc bn học giỏi!@@
ban oi dung bai minh vua lam de minh giai cho
1, =3.[2.(-2)]mu2(thong cam minh ko biet viet mu)+2.(-5)+2mu2nhan-5=3.2mu2.(-2)mu2+2nhan-5+2.2.5=2.[3.2.(-4)+(-5)+2.(-5)=2.(-39)=-78
