Question

初一下：四道数学计算题 求解答~谢谢

1. -3x^2×（-2x^2+1/4x-1）
2. (-5x^2)×(-2y)+3xy(1-3x)
3. (-4a^2b)^2×(1/2a^2b^2-3ab-5b^2)
4. 5x^3×x^2+(-3x^3)^2-(-x^2)^3

Answer 1

1. -3x^2×（-2x^2+1/4x-1）
=6x^4 - (3/4)·x³ + 3x²
.
2. (-5x^2)×(-2y)+3xy(1-3x)
=5x²y +3xy-9x²y
=-4x²y +3xy
=xy(-4x+3)
.
3. (-4a^2b)^2×(1/2a^2b^2-3ab-5b^2)
=-2a^4·b^4 + 12a³b³ + 20a²b^4
.
4. 5x^3×x^2+(-3x^3)^2-(-x^2)^3
=5x^5 + 9x^6 +x^6
=5x^5 + 10x^6
=5x^5·(1+2x)

Answer 2

1. -3x^2×（-2x^2+1/4x-1）
=6x^4-3x^2/4x-1

2. (-5x^2)×(-2y)+3xy(1-3x)
=10x^2y-9x^2y+3xy
=x^2y+3xy

3. (-4a^2b)^2×(1/2a^2b^2-3ab-5b^2)
=16a^4b^2 × 1/b(2a^2b-3a-5b)
=16a^4b/2a^2b-3a-5b

4. 5x^3×x^2+(-3x^3)^2-(-x^2)^3
=5x^5+9x^6+x^6
=5x^5+10x^6