Answer:
126 in^2
Step-by-step explanation:
The area of a trapezoid is found by
A = 1/2 (b1+b2) h
A = 1/2 ( 12+16)*9
A = 1/2 (28) *9
= 126
420.00 that's how much he would have saved in a year
Let x be your first alloy
2/5x+7/10(30-x)=1/2(30)
4x+210-7x=150
3x=60
x=20
So, you need 20 lbs of the first alloy, and 10 parts of the second to make 30 lbs of half iron and half silver alloy!
10.
Factor the following:
8 x^2 - 2 x - 10
Factor 2 out of 8 x^2 - 2 x - 10:
2 (4 x^2 - x - 5)
Factor the quadratic 4 x^2 - x - 5. The coefficient of x^2 is 4 and the constant term is -5. The product of 4 and -5 is -20. The factors of -20 which sum to -1 are 4 and -5. So 4 x^2 - x - 5 = 4 x^2 - 5 x + 4 x - 5 = 4 x (x + 1) - 5 (x + 1):
2 4 x (x + 1) - 5 (x + 1)
Factor x + 1 from 4 x (x + 1) - 5 (x + 1):
Answer: 2 (x + 1) (4 x - 5)
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13.
Factor the following:
16 x^2 - 24 x + 8
Factor 8 out of 16 x^2 - 24 x + 8:
8 (2 x^2 - 3 x + 1)
Factor the quadratic 2 x^2 - 3 x + 1. The coefficient of x^2 is 2 and the constant term is 1. The product of 2 and 1 is 2. The factors of 2 which sum to -3 are -1 and -2. So 2 x^2 - 3 x + 1 = 2 x^2 - 2 x - x + 1 = -(2 x - 1) + x (2 x - 1):
8 x (2 x - 1) - (2 x - 1)
Factor 2 x - 1 from x (2 x - 1) - (2 x - 1):
Answer: 8 (2 x - 1) (x - 1)
How much did he have in the first place ?
