Okay. When it comes to multiplying decimals, you multiply them just like you would do whole numbers. However, solving them by paper, you would add a decimal point into the answer, depending on how many numbers are behind the decimal point in the numbers being multiplied. In this case, the decimal point will go in front of two numbers, because there are two numbers behind the decimal point in -1.2 and 0.4. Know that the answer will be negative, because there is one negative and one positive number.
Multiply both numbers. -1.2 * 0.4 is -0.48. There. The product is -0.48.
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
