Toán Lớp 6: a,2 × x – 5 = 0
Tính hợp lí
b,128 × ( 278-302 ) + 278 × ( 302 – 108 )
c, (-65) + 28 + (-35 -128)
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Toán Lớp 6: a,2 × x – 5 = 0
Tính hợp lí
b,128 × ( 278-302 ) + 278 × ( 302 – 108 )
c, (-65) + 28 + (-35 -128)
Comments ( 2 )
Giải đáp:
a)
2×x-5=0
⇒2×x=5
⇒x=5÷2
⇒x=5/2
Vậy x=5/2
b)
128×(278-302)+278×(302-108)
=128×278-128×302+278×302-278×108
=(128×278-278×108)+(-128×302+278×302)
=[278×(128-108)]+[302×(-128+278)]
=278×20+302×-150
=5560+45300
=50860
c)
(-65)+28+(-35-128)
=-65+28-35-128
=(28-128)-(65+35)
=-100-100
=-200
a,2 × x – 5 = 0
2 × x = 0 + 5
x = 5 : 2
x = 2,5
Tính hợp lí
b,128 × ( 278-302 ) + 278 × ( 302 – 108 )
= 128 × 278 – 128 × 302 + 278 × 302 – 278 × 108
= (128 + 302 ) – 128 × 302
c, (-65) + 28 + (-35 -128)