The student's answer is wrong. When a point (a, b) is reflected across the line y=x, the coordinates of the new point is reversed to (b, a). So D(2, 5) would become (5, 2), E(6, 4) would become (4, 6), and F(3, 3) is still (3, 3). None of the new points is (2, -5).
Correct option is C) A² - B² + BA – AB
Step-by-step explanation:
(A+B)(A−B)=A(A−B)+B(A−B).........because matrix product is distributive.
=A² + BA - AB - B²
And as matrix product is not commutative, so AB¦=¦BA
Hence option C is correct.
Answer:
r = 9
Step-by-step explanation:
Given that c varies directly as (r + 1) then the equation relating them is
c = k(r + 1) ← k is the constant of variation
To find k use the condition c = 8 when r = 3, then
8 = k(3 + 1) = 4k ( divide both sides by 4 )
2 = k
c = 2(r + 1) ← equation of variation
When c = 20, then
20 = 2(r + 1) ← divide both sides by 2
10 = r + 1 ( subtract 1 from both sides )
9 = r
Go over 9x and that should be it
