Given that one root of the equation x ^ 2-6x + C = 0 about X is the square of the other root, find the value of C

Given that one root of the equation x ^ 2-6x + C = 0 about X is the square of the other root, find the value of C

Let the two roots be a, a & sup2 respectively;
From Veda's theorem
a+a²=6
a²+a-6=0
(a-2)(a+3)=0
A-2 = 0 or a + 3 = 0
A = 2 or a = - 3
A & sup2; = 4 or a & sup2; = 9
(1) When two are 2,4, C = 2 × 4 = 8
(2) When the two are - 3,9, C = - 3 × 9 = - 27
The value of C is 8 or - 27

1: How much is 2 / 5 tons more than 3 / 4 tons? 2: a number is 5 times more than 17.5, 2.5 more than 17.5, what is the number (using the equation)

1 3 / 4 + 2 / 5 = 23 / 20 tons
Let this number be X
5X-17.5=2.5
X=4

I don't know how to make an equation. Please do it for me. 1. Five times of a number plus three times of this number equals 4.8
② A number less than six times a number is 4.5. What's the number

1.5x+3x=4.8
x=0.6
2.6x-0.9=4.5
x=0.9