It is known that a = 3x square - 5x + 2, B = 4x square - 5x + 6. Try to determine the size relationship between a and B, and explain why?

It is known that a = 3x square - 5x + 2, B = 4x square - 5x + 6. Try to determine the size relationship between a and B, and explain why?

A-B=-x²-4≤-4＜0;
So a < B
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How to solve the problem of 3x - 0.5x = - 10

2.5x = - 10 (merge similar items)
X=-4

-3x + 0.5x = 10

-3x+0.5x=10
-2.5x=10
x=10÷(-2.5)
x=-4

If (3x + 31) △ 0.4 = 100, that is 5x + 7=______ ．

（3x+31）÷0.4=100（3x+31）÷0.4×0.4=100×0.4              3x+31=40           3x+31-...

What is the simple calculation of 38 × 101-38?

=38×101-38×1
=38×(101-1)
=38×100
=3800

How can 78 × 7.2 78 × 2.7 7.8 be easily calculated?

78*7.2+78*2.7+7.8
=78*(7.2+2.7)+78*0.1
=78*(9.9+0.1)
=78*10
=780

Calculation: 8.78 ^ 2-8.78 * 7.22

8.78^2-8.78*7.22
=8.78x(8.78-7.22)
=8.78x1.56
=13.6968
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Eight ninths of a number is two less than four fifths of 18.5. What's the number?

(18.5 * (4 / 5) - 2) / (8 / 9) - the difference of 18.5 times 4 / 5 minus 2 divided by 8 / 9
＝（14.8-2）/（8/9）
＝12.8/（8/9）
＝14.4

Decompose 12,16,20,24,15,30,35,33,36,48,60,18 into mass factors

12＝2×2×3
16＝2×2×2×2
20＝2×2×5
24＝2×2×2×3
15＝3×5
30＝2×3×5
35＝5×7
33＝3×11
36＝2×2×3×3
48＝2×2×2×2×3
60＝2×2×3×5
18＝2×3×3

1 + 2 = 3,4 + 5 + 6 = 7 + 8,9 + 10 + 11 + 12 = 13 + 14 + 15. What is the regular formula?

n^2+(n^2+1)+…… +(n^2+n+1)=(n^2+n+2)+…… +(n^2+2n)
n=1,2,3……