2+4+6+...+X=60
(2+X)xX/2=120
(2+X)xX=120x2
2xX+XxX=120
Vì X chẵn nên ta thử như sau:
X=10 suy ra XxX+2xX=100+20=120(đúng)
X=8 suy ra XxX+2xX=64+16=80(loại)
Suy ra X=10 (vì nếu X càng bé (<8) thfi đáp số không thế bằng 120)
1 Tim x biet:
a, 2+4+6+.....+ x =240
b,1+2+3+......+x=306
tim a/b biet a/b x 4 + 1/6 = 17/6
tim phan so a/b biet a/b x 4 = 1/6 = 17/6
2. Tim x tren y biet
a. x/y + 4/5 = 8/6
b. x/y - 4/5 = 2/3
c. 5/8 * x/y = 5/12
d. x/y : 2/9 = 3/8
Giup minh voi tim x biet
5/3 - 1/3 : ( 1 - x . 1/3 ) = 7/6
3 - ( x : 1/2 +3/2 ) - 1/4 = 1/2
2. tim x biet
a)8/x= 40/45
b)2/5 + x/7=5/6
Bai 1: Tim ab ; biet ab = b x 9
Bai 2 : Tim ab, biet :
a) ab x 5 = 2ab b) ab = 4ab / 9.
Bai 3 : Tim ab, biet : a 2 = b x 5
Bai 4 : Tim cac so ab biet :
a) a x3 = bx9 b) a x4 = b x6.
Bai 5 :
a) Tim abc, biet a , b , c khac nhau va : a x bc = 91.
b) Tim a , b , c khac nhau biet aa x bc = 1001
tim x biet : ( x + 1/2 ) + ( x + 1/4 ) + ( x + 1/8 ) + ( x + 1/16 ) = 1
tim x biet
128 - 3 ( x + 4 )=25 - 2
( 15 - 6 x ) =3
24 + 5 nhân x = 49
219 - 7 ( x + 1 ) = 100
ai nhanh mk tick
kb nha
