Question

去括号,并合并同类项

1/3(3-5a)-4(a/3-1)

3(ab-2c)+(-ab+3c)

7(p-2q)-2(-3p-7q)

2/5*π(5R^2-r^2)-3/5πr^2

Answer 1

解：1/3(3-5a)-4(a/3-1)
=1-5a/3-4a/3+4
=(1+4)+(-5a/3-4a/3)
=5-3a

3(ab-2c)+(-ab+3c)
=3ab-6c-ab+3c
=(3ab-ab)+(-6c+3c)
=2ab-3c

7(p-2q)-2(-3p-7q)
=7p-14q+6p+14q
=(7p+6p)+(-14q+14q)
=13p

2/5×π(5R²-r²)-3/5πr²
=2πR²-2/5πr²-3/5πr²
=2πR²-(2/5πr²+3/5πr²)
=2πR²-πr²

追问

去括号

追答

1题：去括号
1/3×3-1/3×5a-4×a/3-4×(-1)
=1-5a/3-4a/3+4

2题：去括号
3×ab-3×2c-ab+3c
=3ab-6c-ab+3c

3题：去括号
7×p-7×2q-2×(-3p)-2×(-7q)
=7p-14q+6p+14q

4题：去括号
2/5×π×5R²-2/5×π×r²-3/5πr²
=2πR²-2/5πr²-3/5πr²