Answer:
B
Step-by-step explanation:
Remark
The easiest way to do this is to Substitute for y in the top equation.
2x + 4y = 18 Divide by 2
2x/2 + 4y/2 = 18/2
x + 2y = 9
Substitute -3x + 2 in for y in the equation above
x + 2(-3x + 2) = 9
x - 6x + 4 = 9
Combine like terms on the left
-5x + 4 = 9
Subtract 4 from both sides.
-5x + 4-4 = 9- 4
-5x = 5
Divide by -5
-5x/-5 = 5/-5
x = - 1
That makes A and C incorrect.
y = -3x + 2
y = -3(-1) + 2
y = 3 + 2
y = 5
The correct answer should be (-1,5) which is B
The sum of cubes is given as:
a³ + b³ = (a + b)(a² - ab + b²)
Example for the sum of cubes:
64x³+y³ ⇒ This is the sum of cubes because each term; 64, x³, and y³ are cube numbers
By writing each term as an expression of cube numbers, we have:
(4x)³ + (y)³ ⇒ 64 is 4³
Use the factorization of the sum of cubes, we have:
(4x + y) ( (4x)²- 4xy + y²)
(4x + y) (16x² - 4xy + y²)
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The difference of cubes can be factorized as:
(x³ - y³) = (x - y)(x² + xy + y²)
Example
(125x³ - 8y³) = (5x - 2y) ((5x)² + (5x)(2y) + (2y)²)
= (5x - 2y) (25x² + 10xy + 4y²)
1/3 of 30 would be 10. So 10 students walk to school.
