Question

まいまい

（2）で分子を整理する時、なぜ全部をhでくくらずに左のふたつだけくくるのかわかりません、、

h
{(x+h)+2(x+h)}-(x?+2x)
=lim
h→0
h
(2x+2)h+h°
=lim
h→0
h
=lim{(2x+2)+h}
h→0
=2x+2
(2) f'(x)=lim
S (x+h)-f(x)
h→0
h
{(x+h)+3(x+h)}-(x°+3x)
=lim
h→0
h
(3x2+3)h+3xh?+h°
=lim
h
h→0
=lim{(3x?+3)+3xh+h}
h→0
=3x+3
f(x+h)-f(x)
h
(1) f'(x)=lim
h→0
{(x+h)+3(x+h)}-(-x°+3x)
=lim
h
h→0
(-2x+3)h-h。
=lim
h
h→0
=lim{(-2.x+3)-h}
h→0
=12.x+3
三
f(x+h)-f(x)
h
(2) f'(x)=lim
h→0
{2(x+h)+(x+h)}-(-2x+x)
=lim
h
h→0
(-2+3x°)h+3.xh°+h°