(1)原式=42-522+322=32;
(2)原式=52×22-2×3×32=20-3=17.
The skin, an ____ part of your body and its largest organ, ____ as a barrier against diseases.[ ]
A. vital, acting
B. vital, acts
C. essential, acting
D. essential, acts
胀接是利用胀管器使管子端部在管板孔内产生()变形,从而具有抗泄漏的严密性和抗拉脱强度,以达到密封和坚固连接的目的。
A、弹性
B、塑性
C、韧性
D、柔性