Answer:
Sister = 15 years old
Brother = 12 years old
Step-by-step explanation:
Right now, if the brother is B years old and the sister is S years old, B = (4/5)S because the ratio from brother to sister is 4:5, so if one unit is X, B = 4X and S = 5X
Three years ago, the brother was B-3 years old and the sister was S-3 years old. Keeping one unit as X, we have
B = 3X
S = 4X
B-3 = (3/4)(S-3)
Therefore, we have a system of equations
B = (4/5)S
B-3 = (3/4)(S-3)
Substitute (4/5)S for B into the second equation to only have one variable
(4/5)S - 3 = (3/4)(S-3)
(4/5)S - 3 = (3/4)S - 9/4
add 3 to both sides and subtract (3/4)S from both sides to isolate the variable and its coefficient
(1/20)S = 3/4
multiply both sides by 20 to isolate the S
S = 15
B = (4/5)S = 12
Answer:
£210
Step-by-step explanation:
I think i just worked it out in my head
Answer:
The result will be: 5x³ -11x² -9x + 18
The answer is (-∞.∞).
Draw out a number line. Plot 0 and -4 on the number line.
Shade to the left of x = 0, and have a filled in circle at the endpoint. This is the graph of x≤0
Then graph x ≥−4 by plotting a filled in circle at -4, and shading to the right.
Note how the two graphs overlap to cover the entire real number line
So if we have x≤0 or x≥−4 then we're basically saying x is any real number. To write this in interval notation, we write (−∞,∞)
This is the interval from negative infinity to positive infinity (or just infinity). We exclude each endpoint because we can't actually reach infinity itself. Infinity is not a number. Infinity is a concept
Side note: if you change the "or" to "and", then the solution to x≤0 and x≥−4 would be [-4, 0][−4,0] to indicate the interval from x = -4 to x = 0, including both endpoints. This is the region where the two graphs overlap.
To know more about graphs
visit-:brainly.com/question/10712002
SPJ9
