中一MATHS,,解答者..真的thz t_t (+10)

1) 3(y)+4(3y)=105............their total length
3y+12y=105
15y=105
y=7

so the length of the square=3(7)
=21cm

the area of the sauare
=21(21)
=441cm^2


2) let the three consecutive numbers be x,x+1,x+2

x+(x+1)+(x+2)-4(x)=1
3x+3=4x+1
2=x
x=2

so the three numbers are 2,2+1,2+2
are 2,3,4

a wire with length 105cm is cut into two.they are bent to form an equilateral triangle with lengths y cm and a square with lengths 3y cm.find the area of the square.

Triangle → 3y cm
Square → 12y cm
3y + 12y = 105
　　15y = 105
　　　y = 7
　The area of the square
= ( 3y ) ²
= ( 3 * 7 ) ²
= 21 ²
= 441 cm²

The sum of three consecutive numbers minus4 times the smallest numbetr equals 1.
find the three number.

Let x be the smallest number
x + (x+1)+ (x+2) = 4x+1
　　　　3x + 3 = 4x+1
　　　　　3 - 1 = 4x - 3x
　　　　　　x = 2
The smallest number is 2
The thre consecutive numbers are 2 , 3 , 4