求答案Canotta 3+3 Mathematics

Answers as follows:


14) 4x - 5y = 0

4x = 5y

x : y = 5 : 4

Let x = 5k, y = 4k ( k is non-zero )

( 3x - y ) : ( 2x + 3y )

= [ 3( 5k ) - ( 4k ) ] : [ ( 2( 5k ) + 3( 4k ) ]

= 11k : 22k

= 11 : 22

= 1 : 2
=====


15) a : b = 2 : 3 = 8 : 12

b : c = 4 : 5 = 12 : 15

a : b : c = 8 : 12 : 15

By simplicity, ( 3a - b ) : ( b + 2c )

= [ 3( 8 ) - ( 12 ) ] : [ ( 12 ) + 2( 15 ) ]

= 12 : 42

= 2 : 7
======


16) 2x = 3y = 4z

L.C.M. ( 2, 3, 4 ) = 12

Divide each number by 12. We have

x/6 = y/4 = z/3

x : y : z = 6 : 4 : 3

Let ( x, y, z ) = ( 6k, 4k, 3k ), k non-zero

( x - y + z ) : ( x + y - z )

= ( 6k - 4k + 3k ) : ( 6k + 4k - 3k )

= 5k : 7k

= 5 : 7
=====


17) a : b = 3 : 5 = 9 : 15

b : c = 3 : 2 = 15 : 10

a : b : c = 9 : 15 : 10

( 2a + 3b - c ) / ( 3a - 2b + c )

= [ 2( 9 ) + 3( 15 ) - ( 10 ) ] / [ 3( 9 ) - 2( 15 ) + ( 10 ) ]

= 53 / 7
=======


Hope I can help you.

i want all answer