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BỘ ĐỀ THI THỬ THPTQG NĂM 2018 - MÔN TOÁN - MẪN NGỌC QUANG (ĐỀ 1-15) - CÓ LỜI GIẢI CHI TIẾT

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Câu 32: Đáp án C.<br />

u ki n: x 0.<br />

<br />

2 2<br />

log3 x log<br />

1<br />

2x log3 x log3 2x 0 log3<br />

2x 0 0 2x<br />

1<br />

3<br />

a 0<br />

2<br />

2 <br />

2 1<br />

0 x 2 a b 0<br />

2 <br />

2 <br />

b<br />

2<br />

2<br />

2 2 2<br />

<br />

Câu 33: Đáp án D.<br />

1 1 1 <br />

y' 1.ln x x. ln x 1 0 ln x 1 x ; e<br />

x e 2 <br />

e <br />

y 1 ln 2 1 1 1 1<br />

; ; ; min <br />

2e 2e y e e y e e M Maxy e m y e<br />

Câu 34: Đáp án B.<br />

3<br />

2 1000<br />

<br />

1. 2<br />

p <br />

<br />

3 1<br />

u p<br />

<br />

3 1<br />

3<br />

<br />

4 2 S1000<br />

<br />

u1. p 54 u1<br />

<br />

4 6<br />

3<br />

Câu 35: Đáp án D.<br />

0 0<br />

<br />

x 2e y 2eln 2e 1 2e<br />

1 ln 2 1<br />

1000<br />

1<br />

y ' 1.ln x x. ln x 1 y ' 2e ln 2e<br />

1 ln 2 2<br />

x<br />

ơ ế ế x<br />

0<br />

y y'<br />

x x x y <br />

0 0 0<br />

Câu 36: Đáp án C.<br />

Câu 37: Đáp án A.<br />

x 1<br />

5x 1<br />

Ta có: lim<br />

x3<br />

x 4x 3<br />

ln 2 2 x 2e 2e 1 ln 2 1 2 ln 2 x 2e 1.<br />

R a<br />

2<br />

Suy ra a = 9, b = 8 a b = 1.<br />

Câu 38: Đáp án A.<br />

2 2 2 2<br />

MA MB MC MD<br />

3 3<br />

3<br />

<br />

a a<br />

4 4<br />

V R <br />

3 3 2 6<br />

<br />

<br />

<br />

<br />

x 4x 3 x 3 . x x x 4x<br />

3 9<br />

lim lim .<br />

x<br />

3 x<br />

x 1 5x 1 x 3 x 1 3 x 1 x 1 5x<br />

1<br />

8<br />

MG GA MG GB MG GC MG GC <br />

2 2 2 2

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