Answer:
D
Step-by-step explanation:
The equation of a circle centred at the origin is
x² + y² = r² ( where r is the radius )
Here r = 15, thus
x² + y² = 15² , that is
x² + y² = 225 → D
Answer:
Step-by-step explanation:
To factor the equation, break it into two binomials which multiply to make the equation. To write these binomials (x+a)(x+b), find factors which multiply to -20 and add to -1 for a and b.
20: 1, 2, 4, 5, 10, 20
-5+4 = -1
Answer:
x = -2, y = -4
coordinate: (-2, -4)
Step-by-step explanation:
Given system of equations:
a) 4x - 7y = 20
b) x - 3y = 10
1. Make x the subject in the <em>second</em> equation:
⇒ x - 3y = 10 [add 3y to both sides]
⇒ x - 3y + 3y = 10 + 3y
⇒ x = 3y + 10
2. Substitute the given value of x into <em>first</em> equation:
⇒ 4x - 7y = 20
⇒ 4(3y + 10) - 7y = 20 [distribute 4 through the parentheses]
⇒12y + 40 - 7y = 20 [combine like terms]
⇒ 5y + 40 = 20 [subtract 40 from both sides]
⇒ 5y - 40 - 40 = 20 - 40
⇒ 5y = -20 [divide both sides by 5]
⇒ 5y ÷ 5 = -20 ÷ 5
⇒ y = -4
3. Find the value of x by substituting the given value of y into x = 3y + 10:
⇒ x = 3y + 10
⇒ x = 3(-4) + 10 [multiply]
⇒ x = -12 + 10 [add]
⇒ x = -2
4. Check your work:
<em>a) 4x - 7y = 20</em>
⇒ 4(-2) - 7(-4) = 20
⇒ -8 + 28 = 20
⇒ 20 = 20 ✔
<em>b) x - 3y = 10</em>
⇒ -2 - 3(-4) = 10
⇒ -2 + 12 = 10
⇒ 10 = 10 ✔
This system of equations has a solution at (-2, -4).
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each diagonal cuts the other into two equal parts.
