Let...
x=the number of red bricks
y=the number of blue bricks
Since she bought a total of 100 bricks... x+y=100.
Because the total cost is $560... 5x+7y=560.
Using these two equations, we can use the substitution method to solve for x and y.
x+y=100 ------------------------> x=100-y
subtract y on both sides
Because x=100-y...
this is x
5x+7y=560 (second equation) equals 5( 100 - y )+7y=560
This equation we created has only one variable so we can solve it.
5(100-y)+7y=560
500-5y+7y=560
2y+500=560
2y=60
y=30 blue bricks
Because x=100-y... x=100-30=70 red bricks.
Step-by-step explanation:
x² + 2x - 5 = 0
that is the same as
x² + 2x + 1 = 6
(x + 1)² = 6
x + 1 = ±sqrt(6)
x = -1 ± sqrt(6)
x1 = -1 + sqrt(6)
x2 = -1 - sqrt(6)
n² - 20n + 2 = 4
this is the same as
(n - 10)² = 102
n - 10 = ±sqrt(102)
n = 10 ± sqrt(102)
n1 = 10 + sqrt(102)
n2 = 10 - sqrt(102)