<span>Last
year, the average math SAT score for students at one school was 475. The
headmaster then introduced a new teaching method hoping to improve scores. This
year, the mean math SAT score for a sample of students was 491. The headmaster
concluded that the new teaching method produces higher SAT scores. The problem
with reporting results this way is voluntary response. The information of how
the teaching method isnot mentioned.</span>
Hi friend,
This is a perfect square trinomial.
It can be recognised because it is of the form:
a^2−2ab+b^2=(a−b)^2
with a=3x and b=4
9x2−24x+16=(3x)2−(2⋅(3x)⋅4)+42
=(3x−4)2
Answer:
b
Step-by-step explanation:
∠ BAD = 90° and
∠ DAC + ∠ CAB = ∠ BAD, that is
x + 2x - 30 = 90
3x - 30 = 90 ( add 30 to both sides )
3x = 120 ( divide both sides by 3 )
x = 40 → b
U = - 4 i + 1 j
v = 4 i + 1 j
| u | = √ (-4)² + 1² = √ 17
| v | = √4² + 1² = √ 17
| u + v | = √(u + v)²=
= √( u² + 2 u v + v² )= ...
cos ( u, v ) = (-16+1) / (|u| |v|) = -15/17
...= √(17 + 2 · √17 · √17 · ( -15/17) +17) =
= √ 34 - 30 = √ 4 = 2
Answer: C ) 2
