Question

几道简单的高中数学的英文题求解！！！（要详细过程，谢谢）

1. If tan 4x = 2 cot 4x and 0 ≤ x ≤ 180°, then x =(A) 13.7°(B) 54.7°(C) 13.7° and 76.3°(D) 13.7° and 103.7°(E) 13.7°, 76.3°, 103.7°, and 166.3°
2. If 12 sin2 x + sin x − 1 = 0 over the interval 180° ≤ x≤ 360°, then x =(A) 14.5°(B) −19.5°(C) 194.5° or 344.5°(D) 199.5°(E) 199.5° or 340.5°
3. The product of 45,454,545,454,545 and 1,234 containshow many digits?(A) 14(B) 15(C) 16(D) 17(E) 184. Which of the following describes the right and leftbehavior of the graph of f(x) = −3x7 + 2x5 − 3x + 6?(A) Rises right and left(B) Falls right and left(C) Falls left, rises right(D) Rises left, falls right(E) Cannot be determined
5. The expression (x^2+3x-4)/(2x^2+10x+8) is undefined for what value of x?
A. x={-1,-4}
B. x={-1}
C.x={0}
D.x={1,-5}
E.x={0,1,4}

Answer 1

1、两边同时乘以tan4x，化成tan4x*tan4x=2即可
2、因式分解（4sinx-1)(3sinx+1)=0,解方程即可。
3、前边的数*2不进位，*3或*4进位不超过1位，所以只需考虑乘以1000的位数
4、求导得-21x^6+10x^4-3，x绝对值>1时是负的，绝对值<1时-3决定了也是负的，所以两边都递减
5、无意义的x值是指分母=0，（x+4)(x+1)=0