Chứng tỏ
1)(a – b + c) – (a + c) = -b
2) (a + b) – (b – a) + c = 2a + c
3)- (a + b – c) + (a – b – c) = -2b
4)a(b + c) – a(b + d) = a(c – d)
5)a(b – c) + a(d + c) = a(b + d)
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Chứng tỏ 1)(a – b + c) – (a + c) = -b 2) (a + b) – (b – a) + c = 2a + c 3)- (a + b – c) + (a – b – c) = -2b 4)a(b + c) – a(b + d) = a(c – d) 5)a(b –
By Josephine
1) VT=(a – b + c) – (a + c)
=a-b+c-a-c
=-b=VP
2, VT=(a + b) – (b – a) + c
=a+b-b+a+c
=2a+c=VP
3) VT=-(a + b – c) + (a – b – c)
=-a-b+c+a-b-c
=-2b=VP
4) VT=a(b + c) – a(b + d)
=ab+ac-ab-ad
=ac-ad
=a(c-d)=VP
5) VT=a(b – c) + a(d + c)
=ab-ac+ad+ac
=ab+ad
=a.(b+d)=VP
1)VT=(a – b + c) – (a + c)
=a – b + c – a – c
=(a – a) + (c – c) – b
= -b = VP ⇒Đpcm
2)VT=(a + b) – (b – a) + c
=a + b – b+a + c
=(a +a)+ (b – b) + c
=2a+c = VP ⇒Đpcm
3)VT=-(a + b – c) + (a – b – c)
=-a – b + c + a – b – c
=(-a+ a) +(- b– b)+ (c – c)
=-2b = VP ⇒Đpcm
4)VT=a(b + c) – a(b + d)
=ab + ac – ab – ad)
=(ab– ab) + (ac – ad)
=a(c-d) = VP ⇒Đpcm
5)VT=a(b – c) + a(d + c)
=ab – ac + ad + ac
=(– ac + ac) + (ab + ad)
=a(b+d) = VP ⇒Đpcm.