Answer:
11. 78
12. 4x² - 3x - 1
Step-by-step explanation:
11. Sum of n whole numbers = ½(n² + n)
Multiply
½*n² + ½*n
= n²/2 + n/2
To find the sum of the first 12 whole number, substitute 12 for n into the equation.
= 12²/2 + 12/2
= 144/2 + 12/2
= 72 + 6
= 78
12. Area of trapezoid = ½(a + b)*h
Where,
a = 5x - 4
b = 3x + 2
h = x + 1
Area = ½(5x - 4 + 3x + 2)*(x + 1)
Area = ½(8x - 2)*(x + 1)
Area = ½[8x(x + 1) -2(x + 1)]
= ½[8x² + 8x - 2x - 2]
Add like terms
= ½(8x² - 6x - 2)
= ½(8x²) - ½(6x) - ½(2)
= 4x² - 3x - 1
Answer:
120
Step-by-step explanation:
2 of every 5 trees are pine trees.
2/5 · 300 = 120
120 pine trees are going to be planted in the park.
Answer:
5x= 2x+6
Step-by-step explanation:
5 times a number= 5x
2 times the number=2x
6 more= +6
Answer:
Both lights flash at 1:00
Step-by-step explanation:
they flash together every 2*7=14 minutes
in 60 minutes there are 4*14=56 minutes
they flash together at 1:56
more minutes brings you to 2:00
they flash together at 2:10 (4+10=14)
that leaves 50 minutes left in the hour
they flash three times which uses up 42 minutes
this brings you to 2:52 (10+42=52)
8 more minutes brings you to 3:00
in 6 more minutes (8+6=14) it will be 3:06 and they will flash together
sorry I don't solve this problem
