SAT数学备考经典模拟题训练25

>>SAT数学模拟题：SAT数学备考经典模拟题训练25

>>SAT考试辅导

10. (3x + 2) (2x - 5) = ax² + kx + n .

What is the value of a - n + k ?

A. 5

B. 8

C. 9

D. 10

E. 11

9.Correct Answer: B

Explanation:

Surface area of one small brick = 6; total number of bricks = 12; total surface when disassembled = 6 x 12 = 72

Surface of whole big block= area of four larger faces + area of the two smaller faces = (4 x 6) + (2 x 4) = 24 + 8 = 32

The increase is 40 units

10.Correct Answer: A

Explanation:

This is a quadratic equation. To find n we multiply the last terms in each bracket together (2 times -5) = -10

To find ‘a’ we multiply the first terms in each bracket together (3x times 2x) = 6x2, So a = 6.

Thus a - n = 16

To find k we multiply the first term in the first bracket by the second term in the second bracket and add the result to the product of the second term in the first bracket and the first term in the second. (-15x + 4x) = -11x. So k = -11

16 - 11 = 5

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