先化简,后求值2x-(5x+7)+(7x-2),其中x=3

问题描述:

先化简,后求值2x-(5x+7)+(7x-2),其中x=3

2x-(5x+7)+(7x-2)
=2x-5x-7+7x-2
=4x-9
=4×3-9
=12-9
=3